If Gaeilsinger is still around, the book you refer to is probably Abair Amhrán a book of songs first produced, I think in the late fifties or early sixties, for the use of Irish language enthusiasts.

It contains contemporary translations into gaelic of a whole range of songs, some traditional and others popular songs of the day. Many mistakenly believe that the Gaelic versions are the originals and the english versions are the translations, but quite often this isn't the case. I used to have copies of this book and if I can locate them I'll confirm that this is the book and any information that it might contain aboujt the song, provenance etc, although this is usually very sparse.

As for Sean South (Sabhath), this is a much newer song dating from an incident in 1956, so that song is sung to the Roddy air rather than the other way around.