OK, I don't want to be a wet blanket around here or anything, but here we have scholars as esteemed as Charlie Baum and The Artist Known Only By His Guitar Tuning (DADGBE), and we still don't have a solid answer to the original question. It seems like this is a song that everybody has known forever, but yet we can't find mention of it before Sam Henry's contention that it was heard in Ireland in 1905. Helen Creighton put in in Songs and Ballads from Nova Scotia (1932), but doesn't give a date for it. I believe the tune is often also used for Peter Emberley, isn't it?
So, allow me to repeat the original question - when and where does this song come from?

I've been tempted to do this at our Wednesday night sing, but I'd much rather have DADGBE grace us with his presence and sing his Los Angeles version for us. How 'bout it, Ray?

-Joe Offer in Sacramento-