Maybe the 'Willie' problem stems from the old story that Andy Irvine was looking into Bronson (Tunes to the Child Ballad) for a tune to WoW and picked the 'wrong' one by happy accident. This might have been mentioned in the sleeve notes (by Mick Moloney) to the first Sweeny's Men album - I don't have it to hand so I can't check. However, if others picked it up from such a source, then they can't be blamed for taking the statement at face value. I never heard that he wrote it himself - but of course he may well have done, and not wanted to claim the credit at the time, although I can't think of any reason why this might be, other than the reluctance of some folksingers to admit to 'tampering' with the tradition. But choosing the 'wrong' tune is tampering too, so it can't be that ... can it?

Anyway, the marriage of tune and the words, as recorded on the first Sweeny's, are Andy Irvine's inspired work ( whether deliberate or accidental) and I can see why he might be miffed at people not acknowledging him as the source.