The word comes from Paddy Tunney's version of the song, which is the one that most revival performers sing. See thread The Green Fields of Canada for some discussion which touches on Paddy's occasional poetic additions to songs; it would seem that this is one such. The meaning of the word isn't enlarged upon; it would be whatever Paddy meant it to be.

Unfortunately it isn't any longer possible to ask him, but it's likely enough that people did, and not impossible that someone may come by who remembers.