I am hardly qualified to discuss this point with Gaelic speakers, but curiosity got the better of me, and I had a look at the online version of Alexander McBain,
An Etymological Dictionary of the Gaelic Language (Glasgow: Gairm, 1982, reprint of 2nd edn, 1911), which says:
"
bràghad: neck, throat, Irish
bráighid, Old Irish
bráge, g.
brágat [...]. Bezzenberger (Stokes' Dict.), refers it to the root of Norse
barki, weazand [...].
bràghad is really the gen. of
bràighe.
bràighe: upper part (of places): this is the nom. case of bràghad, which also appears in place names, as Bra'id-Albainn, Braidalbane."
http://www.ceantar.org/Dicts/MB2/mb04.htmlThere seems to be a consensus that Scots
brae is Germanic in origin (from Norse
bra, 'brow'. So it looks as though brae/bràigh is a case of semantic convergence of different words from two separate Norse roots. If this is true (which I cannot judge), it is a curious coincidence, because these words really do look as though one must have come from the other.