Have you looked at Macbain's entry? "It is clear..." doesn't always
mean "it is correct" but this is his contribution FWIW:
<binn>, sentence, verdict; [*bendi-], [*benni-]; cf. E.Ir. [atboind],
proclaims, [*bonno^], I ban. Cf. Skr. [bhan], speak, Eng. [ban].
It is clear that Gaelic has an ablaut in [e:o] connected with
the root [bha], speak.
Dennis King wrote:
> Anyone have the etymology of Scottish Gaelic "binn" = breitheanas; dān,
> bās; judgment, sentence; doom ?