It's a long time since anybody commented on this thread, but I should add my two cents: I have always understood this to be Tommy Makem's song, I never heard anybody else sing it before I heard him singing it, and I cannot believe he would have claimed credit for any song he didn't write. (He wrote so many, and his integrity was famously rock-ribbed.) I would be astonished if anybody can identify an earlier source. The air is, of course, "Up among the heather." - Trevor