Latin -ô / -ônis endings

From: Christopher Gwinn
Message: 7280
Date: 2001-05-08

Does anyone know offhand the PIE etymology of the Latin -ô / -ônis
(gen.) endings?

I am specifically interested in this because some Celtic names are
Latinized with this ending and I am trying to figure out what the
original Celtic form was and whether or not there was a close Celtic
parallel to Latin -ô / -ônis.

- Chris Gwinn