I got the Irish Gaelic lyrics from Ciarán Ó Bréartúin, an Irish musician resident in Italy. He found them in Nancy Calthorpe, "The Calthorpe Collection" (1974). Coincidentally, Nancy Calthorpe was once Ciarán's music theory teacher. Perhaps she wrote the translation? It doesn't seem to be attributed in the collection, as when Ciarán wrote to me he was under the impression that the Irish was the original version, something I very strongly doubt from the flavour of the language.