Weirdly, I have the Barzaz CD and the booklet has lyrics for every song except that one. Maybe they do it as an instrumental.

Is Olole in fact a Breton word? It does not look like one on the surface, and it's not in my Breton dictionary. Given its placement in the song it seems it could be a Proper name or even a nonsense word.

The song in fact has few words as YF Kemener sings it. Just a few couplets and a lot of la-la-la. But my Breton's not good enough to make it out.