Hi Sandy! Hamish MAY have got it from a "real" folksinger, since he was collecting all the place, but his singer, if he had one, may well have got it from a book. It's the "standard" version, I suppose, and I haven't ever heard it much different. Anyway, the "mools" are "moulds" [in British English spelling; you'll miss out the U I imagine in American]-- = the earth of the graveyard. Example from Stevenson's "Weir of Hermiston": "This life's a' disappointment, and a mouthfu' o' mools is the appointed end." [Grim, hey?] I've seen it in the plural in this sense.