An important point is that it has been noted that Hittite, Tocharian
and Germanic (arguably the three most archaic branches of IE) always
have *-o- as the thematic vowel in all persons of the middle.
> *-(o)-G-ai
> *-(o)-dG-ai [?]
> *-(o)-(t)-oi
> *-(o)-mV(s)-(dG)-ai
> *-(o)-dGw-oi
> *-(o)-nt-oi
>
> Miguel Carrasquer Vidal
=======================
Arnaud :
> *-(o)-G-ai
the -G- > H2 is the weak unstressed same thing as in (He-)gh(-o) "me"
This -G- was afterwards reinterpreted as being the morpheme for
medio-passive and was extented to P2 P4 P5.
> *-(o)-dG-ai [?]
Originally : only -t- then reinforced as -t- + -G-
this morpheme fuses P2+P1 original morphemes.
Compare with Berber : P1 : -gh- and P2 : -t- (preterite)
t + velar spirant > sanscrit -th-
> *-(o)-(t)-oi
the -t- is probably an anaphoric refering to the object, from *to
hence it is logical that this -t- should not appear in the
medio-passive, in the most conservative languages.
> *-(o)-mV(s)-(dG)-ai
> *-(o)-dGw-oi
I don't understand what these forms stand for
especially -dGw- ??
Arnaud