Sorry Jim, I was being kind of flip there. My point was that it is probably not a mondegreen for Robert. However, when I first saw it on an Irish ballad I thought, "Abore? They must mean O'Bore." People always strive for things to make sense. When they lack a knowledge of some detail in a song, some reference, they usually alter or fill it in with something that works for them. Phonetically, Abore and O'Bore are akin. Because of that, in a land where so many names are preceded by O', it's the most natural assumption to make. That's why I question why a mondegreen like Abore would persist if it had no basis in tradition, even if it were something lost in immediate memory. In any case, neither sounds like Robert.

Lighter, forget about the a entirely. It is simple past tense of bear, tolerate etc. So it's like Lord bore, as in he bore. Unusual. Maybe something Gaelic? I found this in MacBain's dictionary:

abar- confluence; only in Pictish place names: Old Gaelic (Book of Deer) abbor; Welsh aber, Old Welsh aper, Celtic ad-bero-, root ber; See beir. Modern Gaelic pronounces it obair (so in 17th cent.), which agrees with the Old Welsh oper; this suggests od-bero-, "out flow", as against the "to flow" of ad-bero-. The od is for ud, allied to English out. Aporicum: *ati-boro-n (Holden).