“We Olaf”: Pro[(x-)NP] constructions in Icelandic and beyond

This article discusses and analyzes an unusual construction in Icelandic, with a plural pronoun in the singular reading and a directly juxtaposed or annexed NP (or DP), where, for example, við Ólafur (literally “we.nom Olaf.nom”) means ‘Olaf and I’. We refer to this construction as Pro[NP]. Pro[NP] constructions have been reported for a handful of languages that lack a case system. Icelandic, in contrast, is a case language, and Pro[NP] in this language is case congruent : the pronoun and its NP/DP annex are always in the same case. No such language has to our knowledge ever been described in detail before; we provide the first in-depth investigation of case-congruent Pro[NP]. The article further compares the Icelandic construction to apparently similar constructions, including English we linguists and the Russian type of Pro[x-NP], as in my s Petej (literally “we.nom with Peter.instr”), meaning ‘Peter and I’, showing that the Icelandic construction differs from these, despite having similar (but not identical) semantic properties. We propose that plural personal pronouns consist of two parts: a set of variables, {X, Y}, that determine the form of the pronoun, and an NP annex, which constrains the interpretation of the Y variable. Typically, the annex is phonetically silent (bare plural pronouns), but the Icelandic construction is unusual in that the annex is partly overt, thereby allowing a rare insight into the construction of plural personal pronouns.


Introduction
The constructions exemplified by the Finnish and Russian sentences in (1) are cross-linguistically common. (1) Finnish (Holmberg & Kurki 2019: 244) a. Me mentiin Annan kanssa kaupunkiin. we.nom went.1pl Anna.gen with town 'Anna and I went into town.'/'We went into town with Anna.' Russian (Schwarts 1988a: 242) b. My s Petej poedem. we.nom with Peter.instr will-go.1pl 'Peter and I will go.'/'We will go with Peter.' The constructions in (1) have a plural pronoun accompanied by another NP joined to the pronoun by a connector, meaning roughly 'with'. The connector phrase is a sort of an annex (or a satellite) to the pronoun. The two can typically be either disjoint (as in (1a)) or adjacent (as in (1b) The structure of the article is as follows. In Section 2, we provide a basic description of the Icelandic Pro [NP]. Section 3 discusses two constructions that are ostensibly similar to Pro[NP], the Preproprial Construction ("he/the Olaf") and adnominal pronoun constructions like we linguists, and describes several ways in which they are distinct from Pro [NP]. In Section 4, we analyze the relation between the pronoun and the annex, proposing that it is an indirect head-complement relation, mediated by a silent element that heads the annex (bringing the construction (partly) in line with the Russian/Finnish type of Pro [x-NP]). We refer to this silent element as the lock. In Section 5, we defend our analysis of Pro [NP] and argue that it reveals more general properties of how plural pronouns are constructed and interpreted. Section 6 concludes.

Pro[NP] with singular annexes (including coordinated ones)
In this section we provide a fairly theory-neutral description of the Icelandic Pro [NP] construction with singular annexes (and a singular reading of the pronoun).
Pro [NP] is a productive and general construction in Icelandic. It is thus found for all three persons and all three genders, as illustrated in (4)-(6). As indicated in (5) and (6), third person plural pronouns in Pro [NP] normally require a linguistic antecedent (in contrast to the first and the second person pronouns). Pluralities of mixed third person genders are expressed by neuter, see (6) In passing, we note that Pro [NP] is overwhelmingly more common in the language, in all persons and genders, than coordination of a name and a singular pronoun, such as ég og María 'I and Mary' and María og ég, as confirmed by searches (2019-10-15) in corpora: http://timarit.is/ and http://málheildir.árnastofnun.is. These are written language corpora, but, as far as we can tell, this also applies to the spoken language.
Case congruent Pro [NP] of this sort is found in all three persons in Old Norse as well, 7 and for at least the third person in runic Swedish, as in þau kitilmuntr "they.n Ketilmund.m" = 'Ketilmund and she' (Wessén 1965: 60), suggesting that it is a Proto-Scandinavian or a Proto-Germanic inheritance. It has been completely lost in the modern Mainland Scandinavian languages (Danish, Norwegian, Swedish), but it is found in Faroese, the closest relative of Icelandic, albeit not as robustly as in Icelandic. 8 We limit our description to Modern Icelandic.
Icelandic Pro [NP], then, is found for all persons and genders. It is also free to occur in all four cases (nom, acc, dat, gen) and in all grammatical functions, as subjects (nominative or quirky), direct objects, indirect objects, prepositional objects, possessives, or as dislocated DPs. 9 This is partly illustrated in (7) (there is an acc/dat syncretism in the first person plural pronoun paradigm). (7) a. Okkur Ólafi leiddist. Quirky subject us.dat Olaf.dat bored 'Olaf and I were bored.' b. Hún sá okkur Ólaf.
Direct object she saw us.acc Olaf.acc 'She saw Olaf and me.' c. Hún er vinur okkar Ólafs.
Possessive genitive she is friend our.gen Olaf.gen 'She is a friend of Olaf and me.' Pro [NP]s are also well-formed in ECM infinitives and as controllers of PRO ("she believed us Olaf be intelligent" = 'she believed Olaf and me to be intelligent', "we Olaf tried to win match-the" = 'Olaf and I tried to win the match').
The pronoun shows clear head properties in relation to the annex, controlling agreement at the clausal level. That is to say: the pronoun controls person (1, 2, 3) and number (pl) agreement of the finite verb, as seen in (4)-(6). In addition, it controls number (pl), gender (m, f, n), and case (nom, acc, dat, gen) agreement of adjectival and participial predicates. This is partly illustrated in (8). 7 Old Icelandic distinguished between dual and plural við/vér 'we.du/pl' and þið/þér 'you.du/pl' (a distinction that gradually disappeared in the 14 th to the 18 th centuries, the plural forms becoming honorific and largely obsolete, while the old dual forms became general plurals, including both dual and plural readings, see Guðmundsson 1972 Overall, the plurals þér and vér are much more common in the corpus than are the duals, þið and við (þér about three times as common as þið, vér more than twice as common as við). 8 We have only limited information on Pro [NP] in Faroese. Höskuldur Þráinsson did us the favor of asking a few Faroese colleagues about this, and their answers indicate that the type vit Hjalmar "we Hjalmar" is marked but not excluded, vit báðir Hjalmar "we both Hjalmar" being more natural. See also Lockwood (1955: 115). The third person type teir Zakaris "they Zakaris" seems to be even more marked, but the answers nevertheless indicate that it is not totally alien (as it is in modern Mainland Scandinavian). The type vit báðir Hjalmar "we both Hjalmar" is reminiscent of what Haspelmath (2007: 36) NP] has no readings that plain plural pronouns cannot have. Overtly expressing the annex obviously disambiguates the reference set of the pronoun, but it does not add any reading that the pronoun cannot have by itself, given the right context. We will return to this important issue in Section 5. The order of the pronoun and its annex cannot be reversed: við/þið/þaer/þau María and við/þið/þeir/þau Ólafur but *María við/þið/þaer/þau and *Ólafur við/þið/þeir/þau. As far as we know, this is also commonly true of Pro[x-NP] languages, but, in at least many such languages, the pronoun and its x-NP (or NP-x) annex can be disjoint (as seen for Finnish in (1a); see also Vassilieva & Larson 2005: 111-112 on Russian Pro[x-NP]). This is impossible in Icelandic; the pronoun and its NP annex are always adjacent, locked together, regardless of case and grammatical function. While orders like "we Mary have both been there" and "Olaf had seen us Mary there" are perfect, splitting the annex "Mary" from its pronoun leads to sharp ungrammaticality. This is illustrated in (9)  Also, the pronoun cannot be expanded: *við á Brekku Ólafur "we in Brekka [a farm name] Olaf". In contrast, the annex may be expanded: við Ólafur á Brekku 'we Olaf in Brekka" = 'Olaf in Brekka and I', an issue we will return to in Section 4.
All this might seem to suggest that Pro [NP]s are just regular DPs, with the pronoun as a head or a determiner and the NP annex as its direct complement. However, such an analysis cannot be upheld. For one thing, nouns in Icelandic can, in marked circumstances, precede determiners, as in mynddiskur þessi "DVD this" = 'this DVD', Ólafur þessi "Olaf this" = 'this [person] Olaf', kona sú "woman that" = 'that woman', or kona ein "woman one" = 'one/a woman' (see Sigurðardóttir 2019 on kona ein; see also http://timarit.is for more examples). 10 In contrast, as already stated, the annex in Pro [NP] can never precede the pronominal head, *Ólafur við, suggesting that the structure of við Ólafur is not parallel to the structure of ordinary DPs, such as þessi Ólafur/Ólafur þessi, and so on. We assume that the type Ólafur þessi is derived from the more neutral þessi Ólafur by Ólafur moving out of [ DP þessi Ólafur] and adjoining to the DP, yielding [ DP Ólafur i [ DP þessi __ i ]. Moving Ólafur in this way out of við Ólafur is completely blocked, which is not surprising if the structure of við Ólafur is different from that of þessi Ólafur, an issue we will return to.
Further, as we will see, the connection between the pronoun and its annex in Pro[NP] is rather different from that seen between a head and its direct complement, Pro [NP] instead being parallel to plain plural pronouns. We will return to this. Before we can do so, we need to, first, describe the properties of the annex, and, second, analyze its relation to the pronoun. We will describe the annex in the remainder of this section, turning to the analysis of the pronoun-annex relation in Section 4. In between, in Section 3, we discuss constructions that are seemingly similar to but in fact different from Pro [NP].
The annex in Pro[NP] must normally be part of the common ground, presumably for the same reason as the silent referents of bare plural pronouns must usually be part of the common ground (i.e., in, e.g., we = 'I and x', x must normally be part of the common ground). It is typically a personal name, either a regular one, such as Ólafur, or a simplified/short form, such as Óli. Many other categories are possible as well, though, including short form kinship terms (mamma 'mom(my)', pabbi 'dad(dy)', etc.), domestic animal names (Snati, a dog, etc., with a personification effect), definite animate group noun NPs, often denoting occupations (kennarinn 'the teacher', etc.), and plural noun reciprocals, such as vinirnir 'the friends' and systurnar 'the sisters'. 11 Some of this is illustrated in (11).
we teacher-the go.1pl 'The teacher and I will go.' c. Við strákurinn förum. we boy-the go.1pl 'The boy and I will go.' d. Við systurnar förum.
we sisters-the go.1pl 'My sister(s) and I will go.' We will return to plural annexes, such as systurnar 'the sisters' in (11d), in Section 3.2, focusing on singular annexes in this section. Before proceeding with singular annexes, though, we note that the annex cannot easily be another pronoun, plural or singular: *þið við "you.pl we", *þið ég "you.pl I", *þeir ég/þú "they.m I/you.sg", and so on (in contrast to regular coordination, þið og við 'you.pl and we', þið og ég 'you.pl and I', þeir og ég/þú 'they.m and I/you.sg', etc.). 12 The annex cannot be inanimate, apart from potential but normally quite far-fetched coercion under personification. In a fairy tale and other similar contexts, one could say things like við/þið/þaer bókin "we/you.pl/they book-the" = 'the book and I/you.sg/she', but this is excluded in all regular contexts. Also, even in fairy tales, #við/þið/þaer náttúran "we/you/they nature-the" is aberrant (unless Náttúran would be understood as a nickname for a person). This is parallel to the fact that plain við/þið/þaer 'we/you.pl/they.f', without an overt annex, cannot normally refer to a human referent (the speaker, the addressee, a human non-speaker/non-addressee) and an inanimate or an abstract one, such as a book or nature.
The pronoun itself cannot normally have inanimate referents either. That is natural enough for the first and the second person pronouns, as these must include the speaker or the addressee, but this is also excluded for the third person pronouns, even though they commonly refer to inanimates. For example, masculine þeir 'they' may refer to bátarnir "boats-the.m", bílarnir "cars-the.m", or (albeit slightly more reluctantly) báturinn og bíllinn 'the boat and the car', but, apart from personification in fairy tales and the like, the referent of þeir (or þaer or þau) in Pro[NP] cannot be inanimate: In regular contexts, þeir Ólafur means 'Olaf and he/they', where 'he/they' are male persons; it cannot mean anything like 'Olaf and the boat(s)'; nor can þeir bíllinn "they car-the" be used to mean 'the boat(s) and the car'.
The general rule, then, is that both the pronoun and its annex must have animate referents, normally human. Usually, the pronoun and its annex are companions, relatives or associates of some sort. However, even though this is generally the case, it is not a rule or a restriction, see the example in (12) (stated by a person who had never met Queen Elizabeth).
(13) "I was at the bus station, and there were two other people there, which I had never seen before, ung stelpa ('a young girl') and an old man. Við stelpan ("we girl-the" = 'the girl and I') let the old man enter the bus first." Moravcsik (2003) and Daniel & Moravcsik (2013) assume that Icelandic Pro [NP] is an instantiation of the associative plural, as in Japanese Tanaka-tachi 'Tanaka and his family or friends or associates' and Hungarian Péter-ék 'Peter and his family or friends or associates', where the (silent) associate has a kind of a generic unspecific group reading. 13 While this kind of usage, as in þeir Gunnar(r) "they Gunnar" = 'Gunnar and his follower(s)' is seen in Old Icelandic, it is obsolete in the modern language. Actually, the pronoun and its annex can easily be adversaries or "dissociates", as in (14)  Indefinite singular kennari is ill-formed in Pro[NP]: *Við/þið/þeir kennari "we/you/they teacher". Similarly, indefinite *við móðir "we mother", in contrast to the semantically definite við mamma '(my) mom and I', við móðir mín "we mother my" = 'my mother and I', and við móðirin "we mother-the" = 'the mother and I'. The reason why this is the case is presumably that the annex must be a referential expression and part of the common ground, hence either a contextually salient, that is, definite, common noun NP or a name (or a name-like expression like 'mom'). In a somewhat old-fashioned style, though, some singular formally indefinite occupational NPs can be annexes in Pro [NP]: við prestur "we priest" = 'the priest and I', and so on. The nouns involved typically denote (some of the) traditional occupations in the old farming society: bóndi 'farmer', prestur 'priest', biskup 'bishop', and so on. In all such cases, however, the formally indefinite noun must be semantically definite. Við prestur means 'the priest and I', and not 'a priest and I'. 14 This is thus presumably a reflection of the fact that the suffixed definite article was an innovation in Old Icelandic and is still extending its domain in the modern language (see Nygaard 1906: 34  Many plural annexes are also well-formed in plural pronoun + NP constructions. We will discuss these in Section 3.2, in relation to the we linguists construction, found in English and many other languages. Here, we note that Pro [NP] 15 The semantics of við Ólafur is commonly "unified" (cf. Haspelmath 2007: 33): 'I unified with Olaf', 'I in combination with Olaf', or 'I associated with Olaf'. However, even though this kind of semantics is common for Pro[NP], it is not mandatory. It seems to be derived from coordination semantics at the semantic/pragmatic interface (the C[conceptual]-I[ntentional] interface). Við Elísabet Englandsdrotting in (12) and við stelpan in (13) have only plain coordination semantics, and the pronouns and their annexes in (14) are adversaries and not associates.
Pro [NP] is reminiscent of regular coordination. Ólafur og ég 'Olaf and I' and ég og Ólafur 'I and Olaf' mean more or less the same as við Ólafur in the singular reading of the pronoun; similarly, við kennarinn and við mamma (in the singular reading of the pronoun) mean more or less the same as kennarinn og ég 'the teacher and I' and mamma og ég '(my) mom and I', respectively. Nevertheless, coordination must be kept apart from Pro [NP]. First, while the unmarked reading of við Ólafur is 'I and Olaf', við og Ólafur can only mean 'we and Olaf'. Second, as we have seen, the order in Pro[NP] is irreversible, which makes it syntactically different from coordination, as conjuncts are generally reversible: við og Ólafur = Ólafur og við 'we and Olaf' = 'Olaf and we'. Third, conjuncts do not have any head properties in relation to each other, while the pronoun is the head of Pro [NP]. Fourth, of course, coordination is cross-linguistically widespread, in contrast to Pro [NP].
We will return to the comparison of Pro [NP] and coordination in Sections 4 and 5, where we add further evidence that the relation between the pronoun and the annex cannot be represented syntactically as coordination (whereas there is a silent coordination internal to the annex).

Comparison with other adnominal pronoun constructions
In this section, we discuss adnominal pronoun constructions that are seemingly similar to Pro[NP] but are in fact distinct from it. In Section 3.1, we compare Pro[NP] with a singular pronoun + name construction, type "he Olaf". In Section 3.2, we discuss plural pronouns + plural NPs (types we linguists, we brothers).

Pro[NP] is not a preproprial construction
In this section, we compare Pro[NP] with a construction that at first sight might seem to be a Pro[NP] construction of sorts.
Icelandic, especially in the spoken language, commonly combines singular pronouns and names, as in hann Ólafur "he Olaf" = 'Olaf [you know who I mean]' and hún María "she Mary" = 'Mary [you know who I mean]'. Constructions of this sort are cross-linguistically widespread (some standard, some more colloquial/dialectal, some obligatory, some optional). See Lyons (1999: 121-123) and for example Delsing (1993Delsing ( , 2003; Holmberg and Sandström (2003); Longobardi (1994); Julien (2005); Sigurðsson (2006) ;Alexiadou et. al (2007); Christodulelis (2014). The element accompanying the name is either a singular pronoun (as in Scandinavian) or a singular article (as in, e.g., Greek: o Petros "the Peter"). The singular pronouns/articles in these constructions are often referred to as "preproprial articles" (a term introduced into generative syntax in Delsing 1993). We opt for the term preproprials and refer to the construction as the Preproprial Construction, PrC for short, to clearly distinguish it from Pro[NP] with plural pronouns. 16 The Icelandic PrC has some properties in common with Pro [NP]. The preproprial is a pronoun, the following NP is typically a name, part of the common ground, they are case congruent, the two make up a phrase (DP), free to occur in all cases and syntactic functions, and their order is irreversible: hann Ólafur "he Olaf" but not Ólafur hann (as a single phrase, but grammatical in dislocation constructions, in contrast to *Ólafur við). However, there are also clear differences. First, PrCs are confined to the third person: Ég, Ólafur 'I, Olaf' and þú, Ólafur 'you, Olaf' are not PrCs, but appositional, just as in, for example, English. Second, there is no coordination-like relation between the pronoun and the following NP in PrCs: hann Ólafur cannot mean anything like 'Olaf and he'. Third, the annex in Pro[NP] can easily be an animate common noun, as in við kennarinn 'the teacher and I', þeir kennarinn 'the teacher and he', while this is marginal in PrCs (the reading of hann kennarinn 'he, the teacher' is normally appositional, as English he, the teacher, rather than a PrC reading). Fourth, the pronoun in PrCs does not affect the reference of the PrC phrase. It is an article of sorts, a marker of familiarity (in Icelandic), indicating that the speaker assumes the addressee to know and easily identify the referent in question (a cross-linguistically common property of preproprials, see Christodulelis 2014, albeit subject to cross-linguistic variation, see, e.g., Julien 2005). Crucially, it is not the semantic head or core of the PrC. Hann Ólafur means roughly 'Olaf [you know who I mean]' and can easily be replaced by mere Ólafur, without any change in reference and meaning, pragmatic presuppositions apart.
In Pro [NP], in contrast, the pronoun is the head, and við Ólafur cannot at all be replaced by mere Ólafur. This applies generally, even in topic drop contexts. Icelandic is not a (referential) pro drop language, but informal Icelandic is an extensive topic drop language (Sigurðsson & Maling 2010;Sigurðsson 2011), allowing, for example, sentences like (15a). In Pro [NP], however, the pronoun cannot be dropped, as illustrated in (15b) , and þið Ólafur og Pétur either includes the addressee ('Olaf, Peter, and you') or has an appositional vocative reading: 'you, that is, Olaf and Peter'. In sum, despite the initial similarity of PrC and Pro [NP], these constructions are distinct. Crucially, the pronoun in PrC is a determiner, while it is a true pronoun in Pro [NP], and the latter involves a silent coordination (within the annex, see Section 5), while there is no coordination in PrC. In addition, of course, PrC is cross-linguistically widespread, while Pro[NP] (in contrast to Pro[x-NP]) seems to be exceedingly rare.

Pro[NP] is not a regular adnominal pronoun construction
As previously illustrated, singular annexes in Pro[NP] must always be semantically definite in Modern Icelandic: við málfraeðingurinn "we linguist-the" = 'the linguist and I', but *við málfraeðingur "we linguist", and so on. Indefinite plurals, on the other hand, commonly combine with plural pronouns, as in (16) Postal (1966), Déchaine & Wiltschko (2002), and Höhn (2016: 17 ff., 2017, and the references there). They are cross-linguistically widespread, found in Russian, Swedish, German, English, and many other languages: we linguists, you brothers, and so on. 19 They primarily have reduced relative clause interpretations, with regular plural readings of the pronouns, 'we, who are linguists', 'you.pl, who are brothers', but they can also have a singular reading of the plural pronoun: 'I and other linguists', 'you.sg and your brother(s)', as in You brothers should take better care of your mother (where 'you.sg and your brother(s)' is the prominent reading). It is difficult to tell these readings apart, though. The singular readings might be derived from reduced relative clause readings at the C-I interface rather than being "syntactically independent" readings. Singular readings of plural pronouns in APCs in, for example, English, German, and Swedish (we linguists = 'I and other linguists', etc.), are unacceptable or marginal to some speakers, while natural to others. 20 Inasmuch as such readings are possible, however, they are strictly inclusive, confined to "equals", where the pronoun refers to a subset that is included in the set denoted by the NP-annex (set homogeneity). We linguists is only felicitous if the speaker is a linguist, and you brothers in the reading 'you.sg and your brother(s)', is possible only if the addressee is one of the brothers referred to. The same applies to Icelandic APCs, such as the ones in (16). In contrast, it is a salient property of Pro[NP], such as við Ólafur, that it is non-inclusive: the pronoun is (obviously) not included in the reference set of the annex.
Definite plurals can also combine with plural pronouns in English (as also in, e.g., German and Swedish), as in we the linguists, and so on, but these are typically appositional, 'we, (that is,) the linguists' (and can potentially, albeit less centrally, have a reduced relative clause reading, 'we, who are/were the linguists'). Expressions of this sort are arguably structurally distinct form the we linguists type (see Höhn 2016; 2017, and the references there), but we set this aside here.
Parallel phrases in Icelandic can also have appositional and relative clause readings, but, in addition, they have a Pro[NP] reading; it is thus difficult to draw a sharp line between Icelandic Pro [NP] and Icelandic definite APCs. Við málfraeðingarnir "we linguiststhe", can either have the inclusive reading 'the other linguists and I' (where the speaker is a linguist) or the non-inclusive Pro[NP] reading 'the linguists and I' (where the speaker is not a linguist). This holds generally of plural pronoun + plural NPs where the plural NP is or contains a group noun. See (17).

Inclusive reading
Non-inclusive reading (17) a. við kennararnir 'the other teachers and I' 'the teachers and I' we teachers-the ("I" = a teacher) ("I" = not a teacher) b. við börnin 'the other children and I' 'the children and I' we children-the ("I" = a child) ("I" = not a child) c. við Íslendingarnir 'the other Icelanders and I' 'the Icelanders and I' we Icelanders-the ("I" = an Icelander) ("I" = not an Icelander) Plural pronouns + definite plural noun reciprocals, such as við braeðurnir "we brothers-the", also have both inclusive and non-inclusive readings, meaning either 'my brother(s) and I' (where the speaker is one of the two or more brothers) or 'the brothers and I' (where the speaker is not included in the "brother set"). In contrast, við braeður 'we brothers', with an indefinite noun reciprocal, can only have the inclusive reading, 'my brother(s) and I' (plus a reduced relative clause reading, 'we, who are brothers'). 21 We sum up in (18). Inclusive and non-inclusive pronouns + NPs seem to be distinct constructions. Inclusive plural pronoun + plural NPs (APCs), we linguists and so on, are cross-linguistically common. In contrast, non-inclusive Pro[NP] is rare. Icelandic inclusive plural pronouns + plural NPs can have intonation breaks and appositional readings, við, málfraeðingar 'we, [that is] linguists',/við, málfraeðingarnir 'we, [that is] the linguists', while this is excluded for non-inclusive Pro [NP]. At least when these inclusive constructions do have breaks and appositional semantics, they seem to be structurally distinct from Pro[NP], an issue we will return to in Section 5. When they do not have these properties, they might be structural Pro[NP]s (in Icelandic), but we have not been able to find evidence that bears clearly on the issue, so we leave it at that.
We will disregard inclusive readings in the following and focus on non-inclusive Pro[NP] with a singular annex and a singular reading of the pronoun: við Ólafur "we Olaf" = 'Olaf and I', þið mamma "you.pl mom" = '(my) mom and you.sg', þeir málfraeðingurinn "they linguist-the" = 'the linguist and he', and so on. Such expressions are pure Pro[NP]s. 21 A quick check of corpora, the Gigaword Corpus in http://malheildir.arnastofnun.is and http://timarit.is/ (both 2018-08-22)), shows that the indefinites ("pronoun brothers") are more common than the definite ones ("pronoun bothers-the").
Við braeður and við braeðurnir, in the inclusive reading, have a possessive operator, thus meaning 'my brother(s) and I'. The introduction of the operator seems to be due to the inalienable semantics of the relational noun (it is otherwise absent in Pro [NP]). It is also noteworthy that plural braeður(nir) can have a singular reading in við braeður(nir): 'my brother and I'. This potential singularization is presumably due to the inherent reciprocal semantics of braeður. Informally: brothers = x and y are each other's brother. It is absent in Pro[NP]s that do not contain a noun reciprocal: við kennararnir "we teachers-the" and við mömmurnar "we moms-the" mean 'the (other) teachers and I' and 'the (other) moms and I'.

Conclusion
Pro[NP] is special, not surprisingly in view of its rarity. It is distinct from the preproprial construction ("he Olaf"/"the Olaf"), and it is different from cross-linguistically widespread APCs (we linguists/we, the linguists). In the next section, we discuss the relationship between the pronoun and its annex, suggesting that the relation involves a silent head, which we refer to as the lock.

The relation between the pronoun and the annex: the lock hypothesis
As previously mentioned, the annex in Pro[NP] can be expanded: við Ólafur á Brekku "we Olaf in Brekka" = 'Olaf in Brekka and I'. There are some restrictions on this, though.
While þessi Ólafur 'this [person] Olaf' is well-formed in most contexts, ?við þessi Ólafur is unnatural; we find no examples of this sort in corpora. As þessi 'this' is a determiner, a high D-domain element, this might be taken to indicate that the annex is not a full DP, but, rather, a smaller category, perhaps an nP, a NumP or an Art(icle)P; see the extensive discussion of DP structure in Julien (2005) Olaf and I', is nevertheless more natural than ?við þessi Ólafur; evidently, the name is preferably adjacent to the pronoun. As we have seen, there is a silent or a concealed coordination semantics between the plural pronoun and its annex in Pro [NP]. However, as mentioned in Section 2, there are differences between overt coordination and Pro [NP]. We show some of these in (19).

Pro[NP]
Coordination (19) a. við Ólafur 'Olaf and we/I' við og Ólafur 'Olaf and we/*I' b. *Ólafur við Ólafur og við c. *þeir við "they we" þeir og við / við og þeir d. *þið ég "you.pl I" þið og ég / ég og þið e. #við náttúran "we nature-the" við og náttúran / náttúran og við A plain syntactic solution would be to say that the pronoun is a determiner and that the annex is its direct complement, say, [ DP we [ nP Olaf]], in line with a popular approach to English APCs, such as we/you linguists, initiated by Postal (1966) and reignited by Elbourne (2005) and Collins & Postal (2012), see also for example Vassilieva & Larson (2005), and Höhn (2016;. One could then perhaps assume that við Ólafur is syntactically parallel to [ DP the [ nP man]] and that Pro [NP] readings merely arise at the C-I interface, due to the semantics of plural pronouns. While the direct head-complement approach to APCs has been argued for in many works, including the references above, such an analysis is untenable for Icelandic Pro [NP]. First, as we have seen, the annex can be a larger category than nP, for example an Art(icle)P (see Pfaff 2015), as in við málfraeðingurinn "we linguist-the" = 'the linguist and I', or even a full DP, as in við Ólafur þessi "we Olaf this" = 'this [person] Olaf and I'. Second, there is a sharp contrast between þessi Ólafur/Ólafur þessi and við Ólafur/*Ólafur við. While Ólafur þessi arguably involves movement of Ólafur out of [ DP þessi Ólafur], yielding [ DP Ólafur i [ DP þessi __ i ], such movement out of við Ólafur, yielding *Ólafur við, is ungrammatical, indicating that the structure of þessi Ólafur is different from the structure of við Ólafur. Third, Icelandic plural pronouns do not seem to have any special properties as compared to plural pronouns in related languages, apart from the gender distinctions in the third person (which are, however, also found in many other languages). So, if things were as simple as this, we would expect, first, that Pro[NP] expressions like "we Olaf" and "you.pl mom" should be cross-linguistically widespread, contrary to fact, and, second, that *Ólafur við should be available, also contrary to fact.
There are constructions that do involve a determiner and a name complement, such as English this Mary, not that Mary, or the Mary I know is fun (Matushansky 2006). This is also found in Icelandic, see (21) and (22). These constructions do not have any silent or a concealed coordination semantics and are thus different from Pro [NP] examples such as "we Olaf" and "you.pl mom". There is no question, though, that the pronoun is the head (or the label) in Pro [NP], but its relation to the annex is not a direct head-complement relation. There seems to be some hidden element or elements in the construction.
As Pro[NP] is clearly different from regular direct head-complement relations, we need to develop an alternative understanding of the relation between the pronoun and its annex. We propose that there is instead an indirect head-complement relation between the two, mediated by a silent element that heads the annex. We could refer to this silent head as simply h (for head), F (for functional category), or P or p (for preposition) but we opt for the notion lock instead, denoted as • , to express the fact that the pronoun and the annex are always interlocked, cannot be broken apart. Given this, the structure of Pro[NP] expressions is as sketched in (23); the pronoun is the D head of the whole DP, and the annex is a maximal category • P, headed by the silent lock. (23) The lock may possibly be conceived of as a deficient or a "weak" head in the sense of Chomsky (2015) (or as a silent relator in the sense of den Dikken 2006).
Given this analysis, Icelandic Pro [NP] is structurally parallel to the Russian/Finnish Pro[x-NP] construction type, the difference being that the connector x is overt in Russian and Finnish, thereby making it possible for the annex to move from the pronoun (as discussed for Finnish by Holmberg & Kurki 2019).
As mentioned before, there is also another difference between Icelandic Pro[NP] and Russian/Finnish Pro[x-NP], namely that the Russian/Finnish constructions have or can have comitative semantics, in addition to coordination semantics, while this is excluded for Icelandic Pro [NP]. Evidently, the silent connector, the lock, does not add any semantics, in contrast to the overt 'with' connector in Russian and Finnish. 23 The lock seems to be related to role linkers, such as Icelandic sem, English as, German als, etc., in constructions like She was efficient as a priest/Hún var dugleg sem prestur. This Icelandic sem (as German als, etc.), is a nonassigner of case, which would fit well with the við Ólafur construction. However, the lock is not the same element as the overt role linker or just a silent version of it. First, the overt linker has clear semantic import, while, as we have seen, við Ólafur has no detectable semantics that differ from plain we (in contrast to "we with Peter" in Russian, etc.), apart from the fact that Ólafur specifies or limits the reference set of the pronoun. Second, Icelandic NP 1 sem NP 2 is usually disjoint, much as for example English NP 1 as NP 2 . Third, as related languages have parallel elements, as, als, etc., claiming that the lock is a silent sem would seem to wrongly predict that Pro[NP] should be cross-linguistically common. Fourth, under this sem hypothesis, it would be unclear why the sem element must be spelled out in hún sem prestur 'she as a priest' (and in hún … sem prestur), while it cannot at all be spelled out in Pro[NP]: *við sem Ólafur, and so on. In NP 1 (…) sem NP 2 , the sem-NP 2 phrase exhausts the comparison or the equalization with NP 1 (informally: 'she as a priest [and not (necessarily) as anything else]'). This is excluded for Pro [NP]; it does not compare or equalize the pronoun and the overt annex. The reason for that, in turn, is that the annex also contains a silent conjunct, which means that comparison with the overt annex cannot be exhaustive, see Section 5. So, even though the lock shares some properties with overt sem, the two are distinct.
Having postulated the lock hypothesis, we turn to the analysis of the annex in the next section. The proposed analysis will eventually lead us to hypothesize that bare plural pronouns are Pro[NP]s in a disguise, with a silent lock and a silent annex.
23 Cable (2017) shows that for some speakers there is a proximity requirement on the relation between the pronoun and the NP in its annex in Russian, as a result of the comitative semantics. That is, for these speakers, in a sentence like "we with father went to different stores" = 'father and I went to different stores', the speaker and the father must have gone together to the same different stores; both went together to store A, both went together to store B, and so on. There is no such proximity requirement in Icelandic Pro [NP]. In Við pabbi fórum í mismunandi búðir "we dad(dy) went to different stores", the speaker and the father may either have each gone to different stores or together to the same stores. Cable (2017)  On this account, the construction involves ellipsis or gapping of the first person singular pronoun (ja 'I'), and the overt connector s 'with' provides the conjunct or coordination relation between the silent singular pronoun and "Peter", plus potential comitative semantics. As Icelandic Pro [NP] does not contain any overt connector, and does not have comitative semantics, this analysis does not carry straightforwardly over to Icelandic, but two similar analyses come to mind. They are sketched in (25). The analysis in (25a) was suggested by Sigurðsson (2006); see also Thráinsson (2007: 91-92); Wood (2009). A virtue of the analysis in (25b) is that it conforms directly with the overt order of the pronoun and its annex, and also that the gap is a phrase, [ &P & NP] (on the widely adopted analysis in Johannessen 1998). We believe that (25b) is on the right track and refer to it as the gapped annex analysis.

The gapped annex analysis
Even if the gapped annex analysis in (25b) is on the right track, it is not complete. Consider the apposition structure in (26). Mary and I we come on morrow '(As for) Mary and me, we are coming tomorrow.' In contrast, as we have seen, Icelandic Pro[NP] can never be reversed and the pronoun and its annex are always glued or locked together, cannot be disjoint or split. Thus, Pro [NP] and apposition structures such as Við(,) María og ég 'We(,) Mary and I' are syntactically different. Nevertheless, they are semantically almost equivalent (as the annex in við María contains a silent conjunct, 'and I', etc., see below). They are not entirely equivalent, though, at least not in information structure, as appositions, such as María og ég 'Mary and I' in (26) and (27), are not at issue, in contrast to Pro [NP] expressions (see Potts 2005 on at-issue and not-at-issue expressions). However, it is difficult to tease the two apart, and we will not try to do so here.
The fact that the pronoun and its annex are always interlocked is a central fact of the Icelandic Pro[NP] construction. Any approach to this unusual DP type must come up with a story on this lock effect. We account for it by postulating that Pro[NP] has a silent head between the pronoun and its annex, which we refer to as the lock. At first sight, the lock would seem to be sui generis. However, we propose that the lock is a general property of plural pronouns rather than a special property of Pro [NP]. As mentioned in Section 2, plain plural pronouns can be truth-functionally non-distinct from Pro[NP]: Icelandic við, English we, Russian my, and so on, can refer to 'Mary and I'. 24 Consider (28).
(28) a. Mary and I are coming tomorrow, but we will be late. b. Mary does not really like me, but we get along. c. Mary believes that we will make it in time. d. Mary promised John that we will go there. e. Peter said to Mary that we should be there in time.
The pronoun we does not have to have only the reading 'Mary and I' in all these cases; the relevant point is merely that it can have this reading, raising the question of how this reading is represented in syntax. That it is syntactic (and not merely semantic/pragmatic) is suggested by a number of facts, for example by dual/plural distinctions in many languages (see Corbett 2000), in particular dual/plural agreement distinctions in languages like Gothic and Slovenian, for example Gothic wit nimōs 'we.du [both] take.du' vs. weis nimam 'we.pl [all] take.pl'. English does not have such distinctions in its pronominal and verbal systems, but it does in quantifiers: we both went vs. we all went. While we both can refer to 'Mary and I', we all cannot (in normal language use). That is, when deciding between we both and we all, syntax must "know" whether we refers to "individual x and I", for example 'Mary and I', or "plural x and I", for example 'Peter, Mary and I' or 'they and I'. It seems, then, that the various readings of plural pronouns, for instance the reading 'Mary and I' of we, are read or reconstructed into syntax, before syntax can proceed in making lexical distinctions that depend on the pronominal reading. If so, Icelandic við, English we, Russian my, and so on, can have the same syntactic representation as Icelandic við María 'Mary and I'. We thus propose that plain plural pronouns are syntactic Pro[NP]s, with a silent lock and a silent annex. 25 If so, the lock between the pronoun and its annex in Icelandic Pro [NP] is an inherent property of plural pronouns rather than a specific property of the Pro[NP] construction. The lock can be broken by syntactic and/or PF means. One such means is the introduction of an overt connector in the Russian/Finnish Pro[x-NP] type, and another one is the introduction of intonation breaks in appositional constructions. Accordingly, appositional constructions and Russian/Finnish Pro[x-NP] constructions can be split or disjoint. This suggests that the Russian/Finnish constructions start out with the silent lock, the lock subsequently being broken by with-insertion in syntax or PF.
We hypothesize that spelling out the annex generally breaks the lock, and that Icelandic Pro [NP] is special in being exempted from this lock breaking (while the lock is broken in other Icelandic constructions, including overt comitative constructions, see the next paragraph). If so, the lock is broken in the we linguists type as opposed to pure Pro [NP] constructions, such as við Ólafur. We (,) linguists, as also Icelandic við(,) málfraeðingar(nir) "we(,) linguists(-the)", can have intonation breaks. This is excluded for við Ólafur, við María. Notice that this implies that our indirect head-complement analysis of Pro [NP] does not carry over to APCs of the we linguists type. As the lock is broken in we linguists, it cannot function as a mediating connector; accordingly, we linguists may be analyzed as a direct head-complement construction, as argued by Postal (1966) and many others since.
Much like for example English, Icelandic has a comitative construction with an overt preposition, við ásamt Ólafi 'we.nom along with Olaf.dat' or við með Ólafi 'we.nom with Olaf.dat', but here there is no (effective, unbroken) lock between the pronoun and the PP complement. The pronoun and the PP can be (and most commonly are) disjoint, and the pronoun cannot get a singular reading; the PP does not contain a silent coordination, so it is excluded for við to single out a conjunct within the PP.
Adopting a central idea also pursued in Vassilieva & Larson (2005) (without adopting all their technical details), we conceive of plural pronouns as sets of variables, {X, Y}, as mentioned in Section 1. We describe this in (29), where sp = speaker and ad = addressee (and where the lock addition is ours).
(29) a. we Informally, thus, we usually denotes I & Y, plural you usually denotes singular you & Y, and they usually denotes he/she/it & Y (see Vassilieva & Larsson 2005: 115). The primary X variable is fixed, as the speaker, the addressee, or a non-speaker/non-addressee, but the secondary Y variable is open to interpretation/reconstruction, depending on the context. Before proceeding, we note that this raises the question (not addressed by Vassilieva & Larson 2005) of whether the X and Y variables are syntactic features or "merely" semantic. In the general Minimalist model adopted here (Chomsky 2001 and subsequent), the variables must be syntactic features. In this model, semantics has two sources: syntax, that provides "basic semantics", and pragmatics, that provides "additional semantics", arising at the C-I interface from the interaction of clausal syntax with the context. Plural pronouns are partly context-sensitive, so they can have some pragmatic semantics or interpretations, but their basic semantics is clearly syntactic.
The Y variable can be constrained or specified in a number of ways. Clusivity is a widely discussed specification of this sort (Cysouw 2003;Siewierska 2004;Filiminova 2005): The first person plural pronoun may include or exclude the addressee, as sketched in (30) On this account, the X variable in plural pronouns is singular, thereby licensing singular readings of the silent X conjunct in the NP annex. Inclusive we can have more readings than just the central one in (31), 'you.sg and we', 'you.pl and I', 'you.pl and we' (see Cysouw 2003;Siewierska 2004), but it is difficult to distinguish between these in languages like Icelandic and English, which make no morphological distinctions between these readings; they are perhaps pragmatically derived at the C-I interface. However, if, for example, we = 'you.sg and we', has a special syntactic representation, it can be analyzed as in (32). We find it worth pointing out here that Icelandic plural pronouns seem to be bimorphemic, v-ið, þ-ið, and þ-eir, þ-aer, þ-au. An intriguing thought is that the first element or "morpheme" actually represents the singular X variable in the pronoun, enabling the pronoun to identify and license the singular reading of X within the NP annex, across a lexicalized Y variable. This is clearly not a sufficient condition for Pro [NP] (cf. French n-ous, v-ous, Italian n-oi, v-oi, etc.), but it might be a necessary one. We leave this for future research.
The X variable is already in the pronoun variable set, so a silent copy of it within the annex might seem to be unnecessary. However, there must be a hidden conjunction in the structures, or else the coordination reading could not be derived (recall that there is no such reading in overtly comitative constructions in Icelandic, "we (along) with Olaf", etc.). In our analysis, the hidden conjunction or conjunctions are within the annex. Having the conjunction(s) within the pronominal set instead, between X and Y, is not an option, as this would wrongly eliminate the difference between við and coordinates such as At first sight, it might seem to be a conceivable alternative to have a conjunction between the pronoun and the annex (instead of the lock), but that would make við Ólafur non-distinct from við og Ólafur, which would exclude the central 'Olaf and I' reading. This would also be problematic for the plural reading of the pronoun. Even though this reading is best rendered by the English translation 'Olaf and we' or 'we and Olaf', við Ólafur (við = plural) and við og Ólafur are not equivalent. In við og Ólafur, Olaf is always excluded from the reference set of the pronoun; the pronoun refers to 'I + Z' (=we), where Z explicitly does not include Olaf (just as in English we and Olaf). In við Ólafur (við = plural), in contrast, Olaf is included in the reference set of the pronoun, 'I + Z + Olaf'; the only difference between plain við and við Ólafur is that the annex specifies that Olaf does belong to the reference set of the pronoun.
In sum: Plural pronouns contain a feature variable set, {X, Y}, and coordination semantics. The coordination cannot be within the variable set, as that would conflate plural pronouns and regular overt coordination, you and I, and so on. And in Pro[NP], the coordination cannot be between Pro and NP, as that would exclude the central singular reading of the pronoun. Thus, we conclude, the silent coordinator must be within the NP annex, in both "we Olaf" and in the silent NP annex in plain we/við. Spelling out the whole NP annex, including the coordinator, yields adjunction structures, as in we, Olaf and I and we, you and I, different from both "we Olaf" and plain we/við, and spelling out the coordinator plus or minus Olaf yields ungrammatical *we Olaf and, and *we and.
There is a general restriction on the relation between the X and the Y variables, such that the Y variable cannot include or overlap with the singular referent of the X variable. 27 Thus, we cannot mean "plural speaker", 'I & I' (see Boas 1911;Benveniste 1966;Bobaljik 2008). 28 They can mean 'he/she & he/she', but the two "hes/shes" are not equivalent; the 'he/she' referred to by the Y variable is necessarily distinct from the 'he/she' referred to be the X variable (as sometimes made explicit by gender, as in Icelandic neuter þau, referring to males + non-males or females + non-females (or neuter(s) + neuter(s)). Similarly, even though plural you can mean 'you.sg & you.sg' the two singular "yous" must (obviously) be distinct; the Y variable 'you' cannot include or overlap with the X variable 'you'. As a matter of fact, no language is known to indisputably have a plural pronoun that specifically refers to addressees only, excluding everybody else (Simon 2005;Bobaljik 2008).
Our analysis minimizes the difference between Pro[NP]s and plain plural pronouns, but it does not eliminate it. Without lexical specification, the NP annex is unsaturated, and við can include unlimited salient (primarily human) referents, in addition to the speaker: Olaf, Mary, Peter, and so on. With lexical specification (plus the representation of the X variable in the silent conjunct), the annex is either fully saturated or partly saturated. When fully saturated, any other referents than the lexicalized one (and the silent X variable) are excluded, and við Ólafur then means only 'Olaf and I'. When partly saturated, the lexicalized referent is included, without excluding other potential referents, and við Ólafur then means 'Olaf and we'.

Concluding remarks
We have argued that Pro [NP] constructions are constructed in a way that reflects a more general, deeper property of plural pronouns: that they are constructed from a set of variables and an annex, which is headed by a silent head, the lock, • . The set of variables includes a primary variable, X, identifying the speaker, addressee, or neither, and a secondary variable, Y, which is context dependent and can be constrained or specified by the annex in a number of ways. What is unusual about the Icelandic Pro[NP] construction is that the annex can be partly lexicalized without breaking the lock. In this way, plural pronouns in general have a singular reading of the X variable, one that is usually not made overtly obvious. The overall picture strongly suggests that pronouns do not have meanings that are given in a presyntactic lexicon, but that plural pronouns are built out of features whose interpretation is syntax-/context-dependent. Our analysis also supports the view that silent elements ("dark matter") are pervasive in syntax (as argued in Sigurðsson 2004 and much subsequent work).
Exceptional phenomena often throw new light on the nature of more general phenomena. Icelandic Pro[NP] is highly exceptional, and it does indeed throw new light on the nature of plural pronouns. Our analysis involves some unorthodox ingredients, not surprisingly, in view of these circumstances. At first sight, the lock might seem to be sui generis, but we have argued that it is actually a general property of plural pronouns. In addition, we have argued that plural pronouns, bare as well as in Pro [NP], have a silent copy of the X variable in the NP annex, and that the reading of the X variable is consistently singular. This is a universal property of plural pronouns, we claim.
We have shown that the widely adopted direct head-complement analysis of APCs like English we linguists does not work for Icelandic Pro [NP]. Instead, we have argued that there is an indirect head-complement relation between the pronoun and its annex in the Icelandic Pro[NP] type, mediated by the silent lock, which brings the Icelandic construction in line with the Russian and Finnish type of Pro[x-NP]s, "we with Peter" = 'Peter and I', and so on. The difference is that the overt connector in the Russian/Finnish type breaks the lock between the pronoun and its annex, thereby making it possible for the annex to move from the pronoun, or vice versa.