Well, as a purely speculative idea, how about a derivation from *bhērH-o-
'brown' or *ghuer- 'wild animal' plus *-to / -tā to lexicalize the adj. /
Of course to get beithir there would have to be metathesis of -r- and -t-
to get the desired outcome.
So, a little complicated, but it gets us there.
On Mon, Dec 31, 2018 at 2:08 PM David Stifter <[log in to unmask]> wrote:
> From: Old-Irish-L <[log in to unmask]> On Behalf Of Dennis
> > nathir (Sean-Ghaeilge) < *natrixs (Ceiltis) beithir (Sean-Ghaeilge) <
> *betrixs (Ceiltis) ??
> The examples of beithir that show k-inflection don't have a lot of
> evidential weight. There is a tendency throughout the history of Irish to
> inflect as k-stems all words ending in -thir, this is spreading before our
> eyes. Forms like beithri without -ch, esp. in early texts, are more
> crucial. We can mechanically set up a Celtic preform *betrī or *bete/irī,
> or even *beturī, but that doesn't reveal anything insightful. The word is
> formally reminiscent of beithe 'birch' < *betu̯ii̯o-, but maybe that's just