Thanks GUEST. 1934 fits the chronology very well. Of course Kavanagh could simply have learned the song from anyone without ever having heard any recording. McCormack though was probably the ultimate source. (I have quite a few McCormack tracks on CD but not that one).

Edward Walsh's "Dawning" is in the Penguin Book of Irish Verse, edited by Brendan Kennelly. It's very similar to the one above but probably closer to the original as it was translated directly from Irish, whereas later versions were edited, changed and "improved" all-English efforts.