This has probably been referred to many, many times on cybalist, but I am seeking a definitive answer (and the search function on cybalist gives me trouble because it's hard to isolate this subject matter, I've tried already).
1. What is the origin of Common Slavic *-U the nom./acc. sg. of masc. o-stems? I think I once read that it comes from the accusative *-om which became *-U due to nasalization. But then what about the neuters with *-om (next question)?
2. What is the origin of Common Slavic *-o the nom./acc. sg. of neuter o-stems? I believe I've read that it is held to have come from *-od which is an importation from the pronouns -- correct? But why do neuter s-stems also have *-o in their nom./acc. sg., while retaining *-es- in other cases and numbers?
3. What is the origin of Common Slavic *-u the dative singular of o-stems? How can this go back to *-o:i?
4. What is the origin of Common Slavic *-y the genitive singular and nominative plural of a:-stems? How can this go back to *-a: + *-es/os?
5. What is the origin of the Slavic ending *-e of the dative singular of a:-stems?
6. Why does the genitive plural of a:-stems have no ending in modern Slavic languages?
7. Why do a:-stems have a separate accusative ending, but o-stems do not?
8. Why does OCS have <kamy> "stone" with <-y> from *-o:n, but *-a:m becomes <-o,> (nasalized /o/)? Wouldn't both have evolved from proto-Slavic nasalized *a:?
I hope someone will be willing to answer these questions, as I find the Slavic inflectional endings to be mysterious when compared to the IE endings.
Andrew