The story of Breccan is related in Cormac’s Glossary. He was a merchant
who traded between Ireland and Scotland with fifty corracles. Now there
was a great whirlpool at Rathlin Island caused by the meeting of the
seas, and they formed a caldron vast enough to swallow all Ireland. And
it happened on a time that Breccan and all his corracles were lost and
engulfed in this caldron. Not a man was left to tell the tale of how or
where they had perished. Thus it was that the skull of a small animal
being discovered on the beach, it was brought to the blind poet, who
laying his staff on it obtained the inner vision by which he revealed
the fate of Breccan and his fifty corracles.