Willie Clancy brought the air back from some festival in Eastern Europe where he learned it from an American singer whose name I can't think of right now (somewhere online Jean Ritchie was mentioned but it was someone else). Seán 'ac Donncha chased up the words and put them to Willie's air. Joe Heaney in turn learned it from Seán.
Christy Moore did indeed get his version from Hamish Imlach and one piper quotes Nina Simone as an influence on his version of the air.
That's some of the story of things in Ireland. Niles doesn't get a look in at this stage.