The OBD learned the song from a Pentangle record, not from a traditional source; the tune and refrain don't belong to The Cruel Sister (Child 10) but to Riddles Wisely Expounded (Child 1). This has been discussed many times here in the past, but at the moment the search engine returns no results at all for the Forum (where most of the information is held) so the history of the song-family (which is complicated and extensive) will have to wait just for now. Let's hope that everything starts working again soon, so that we don't wind up repeating everything yet again in this new thread...