The word (pl. баре, ['bа:rʲe]) is roughly rendered into English as 'gentry' meaning 'a noble person without a position at imperial court'. The boyar is possibly not a cognate.
What surprises me the most is that the word bár in Old Irish (especially in its poetic speech, or in bérla na filed) had meant ´a wise chief', while the most ancient Irish sources provide a word for ´bárnía', or ´wise warrior´, and this word is even more resemblant to the Russian ´barin´.
The word барон 'baron' is not a possible source, because it does not coincide with the plural form (бароны <=барон VS барин => баре). However, the plural of боярин is бояре, which suggests a pattern, but does not explain the intervocal [j] in boyar. What is the etymology of boyar, by the way?
Hence, the question is: are there any reliable etymologucal sources (please do not quote any Vasmer or the like) which might help me in shedding some light on this issue?