Where does the 'Einheitsplural' come from?

Gothic pass. ind.
baira-da
baira-za
baira-da
baira-nda
baira-nda
baira-nda

The PIE middle endings are usully reconstructed as
*-mo(i)
*-so(i)
*-to(i)
??
??
*-nto(i)

The ??'s are there because no one reconstructs PIE 1,2pl pass, they
are too different in the individual languages, as if each people found
it's own solution to the problem (so do linguists, they write *-m-,
*-s-, *-t-, *-nt- and pretend that's the whole solution, bad habit).
My own explanation is that those *-m-, *-s-, *-t-, *-n-t- are deictic,
"at me", "at you", "at him", "everywhere" stuck to the verbal noun
which is identical to the stem.
The Goth's solution to the problem of the missing 1,2pl is a
particularly simple one: they substitute 3pl for 1, 2pl, end of story.

The northern West Germanic languages also have "Einheitsplural",
unitary plural identical in all three persons in the active, eg for
the present

Old English 123pl -aT
Old Saxon 123pl -aD, -oD
Old Frisian 123pl -ath
Western Low German 123pl -en
Eastern Low German 123pl -t
Some English dialects(?) 123pl -n

It occurred to me that those languages that have a unit plural in a
dental are those that had a rule -nT- -> -T-, namely OE, OS and OF.
That rule would change 3pl -nT (cf Gothic -nd, Old High German -nt)
into -T. If there was a tendency to substitute 3pl for 1,2pl in
northern West Germanic, as happened with Gothic passive, that would
explain the rest of the story.


Torsten