One thing about fields of Athenry turned up in a thread on the Mudcat - Pete St John's words are only slightly rewritten from a song extant in 1888. The minor shifts in words, whoever made them, are probably an improvement I'd say, but I'd definitely call it a new variant rather than a new song.

Though it's possible that the tune might be original to him.

Either way it's a good song, and I don't suppose whoever wrote it back before 1888 will mind (I think it was a fella called Devlin)