Nechtan ... was Re: Picts, Celts and IE

Way back on Tue Mar 7, 2000 Chris Gwinn wrote:

" *Nechtonos "divine descendant" or "god of the waters" (*Nep-t-on-os
or *Nebh-t-on-os related to Roman Neptune) "

as possibly etymologies for Nechtan.
Could Chris or anyone simply clarify anything about how the development
would occur -- especially in the case of *Nep-t-on-os as I believe that
would be the proper form to also have an association with (Apam)
Napat ??

Sincerely,
Aydan