I think the evidence favours the following account: /-g-/ originally occurred only in the gen.sg. of the masculine and neuter forms of the 'two', 'both', and 'three' collectives, i.e.
dwój/dwoje : dwojego
obój/oboje : obojego
trój/troje : trojego
As far as I can see, these were always declined like "complex" adjectives (with pronominal endings, as also in OCS), hence the /-g-/ in the gen.sg. The higher collectives were originally declined like nouns: <czwór/czworo> (earlier <cztwiór> etc.): <czwora>. The old system was therefore like this:
trój, troja, troje : trojego, troje(j), trojego
czwór, czwora, czworo : czwora, czwory, czwora
Forms like <czworga> are attested from more recent times and seem to owe their origin to contamination (infixed /-g-/ "borrowed" from the more frequently used lower collectives). Other secondary variants include not only gen. <trojega> ~ <trojga> (only the latter remaining in current use) but also such nominatives sg. (no longer used) as <dwojgo, obojgo, trojgo, czworgo, siedmiorgo> etc. Before they disappeared, they gave rise to other analogical case forms with /-g-/, such as the modern dat./loc. <trojgu, czworgu> (for older <trojemu, troim>, <troim, troich>, <czworu, czworym>, <czworze, czworzech>), or ins. <trojgiem, czworgiem> (for older <troim, troimi>, <czworem/czworym, czwórmi>).
The result has been a lot of variation and confusion, making the old system collapse completely. Now we only have the old neuter nom.sg. <troje, czworo> etc. plus a generalised oblique stem with the /-g-/ extension: <trojg-, czworg-> plus appropriate sg. case endings (same as in neuter nouns), and no gender or number distinctions.
troje : trojga, trojgu, trojgiem
czworo : czworga, czworgu, czworgiem
I see no reason to believe that <-ga> in collective numerals should be particularly old. It's simply the generalised extension -g- of pronominal origin plus the gen.sg. ending.
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As regards the origin of -g- (Russian -v-) in the gen.sg. of the Slavic interrogative and non-feminine demonstrative and relative pronouns (with the remarkable exception of archaic c^eso/*c^Iso with its -s-), it's so obscure that any reasonable hypothesis is welcome and worth considering. What do you make of *-j- in feminine pronous? Another hiatus-buster?
Piotr
----- Original Message -----
From: "Miguel Carrasquer" <mcv@...>
To: <cybalist@yahoogroups.com>
Sent: Sunday, January 12, 2003 1:33 AM
Subject: [tied] Polish G. -ga
A question for Piotr, really...
The collective numerals dwoje, troje, czworo, pieNcioro ..., oboje,
kilkoro, ... have a peculiar declension in Modern Polish:
NAV dwoje czworo
G dwojga czworga
DL dwojgu czworgu
I dwojgiem czworgiem
This does not go back to Common Slavic, where these numbers were
declined as o-stem nouns/adjectives (OCS G. dUvoja, c^etvera) or as
definite adjectives [at least those ending in -ojI/-oje] (OCS G.
dUvojego, trojego, obojego).
In Stanisl/aw Rospond's Gramatyka historyczna jeNzyka polskiego, the
origin of the oblique in -g (dwojg-, czworg-) is explained as stemming
from contamination of the two forms dwojego ~ dwoja -> dwoj(e)ga
(elision of -e- aided by the former Polish initial accent). The
references given are P. Zwolin'ski (Geneza tematu -g- w odmianie
liczebników typu dwoje, czworo w jeNzyku polskim, Lwów 1938, and W.
Kuraszkiewicz (O skracaniu polskich form liczebnikowych typu
dwanas'cie, dwojga, Wrocl/aw, 1966).
I don't think this explanation is implausible, but perhaps there are
other possibilities...
In particular, is there any chance the -ga may be original? In
Slovenian and Serbo-Croat, the pronominal/adjectival masc. genitive
ending is -oga/-ega (Slov. tega, njega/ga, koga [but cêsa!], adj.
-ega), against -ogo/-(j)ego in the other Slavic languages (including
Polish).
If my theory about the Slavic pronominal genitive is correct (jego <
uncontracted Abl. *e-od, kogo < Abl. *kWo-od, with insertion of
hiatus-breaking -h- ~ -g- or -w- (Russian /jevó/, /kavó/), then the
presence of analogical forms with ending *-o:d (cf. Latin eo:) such as
*eo:d, *koo:d > jega, koga would not be unexpected.