Edmund, the most likely answer is that it is a modern arrangement where the Irish tune was used. I've known this happen with many German bands who were steeped in Irish (Celtic?) music before they discovered German material. I have a poem by Theodor Storm (19th century, native of the North Sea shores between Hamburg and the Danish border) set to an Irish tune. Very strange when I first heard it! There are others I can't remember just now. (I'll have to supply toadfrog with another set of CDs before long. There is so much I should have sent but didn't!)