Think half the problem is the number of multi-volume collections of songs, mainly 'Soodlum's' and 'Folk Songs popular in Ireland'. They don't actually claim that the songs are Irish but most people buying them assume they are, and if an Irish band covers an English/Scottish song the Irish claim it. I was even in a session in Kerry where someone swore blind that Dougie McLean's (spelling might be wrong) Caledonia was Irish ! Would have thought the name would give it away.