I have 2 theories.
1) The original ending, before the application of Szemerenyi's Law, was *-mes, which was later reduced to *-ms > *-ns
2) The genitive is a late formation and the genitive plural was the original accusative plural. The later accusative plural was a combination of the accusative singular *-m with the nominative plural *-es, which later underwent syncope as above.
--- In cybalist@yahoogroups.com, Oliver Neukum <oliver@...> wrote:
>
> Hi,
>
> this may be a stupid question, but I never found an explanation.
> How can Szemerenyi's law be true if the ending of the accusative plural
> has survived?
>
> Regards
> Oliver
>