We were introduced to the song by Jim's favorite Ken Russell film, the early 80's cult classic- "Lair of the White Worm". The movie is based on Bram Stoker's (Dracula author) novel of the same title , which was in turn based an old Welsh legend which was the basis for a traditonal song, which is likley how Bram Stoker heard of the legend. The film co-stars Hugh Grant (first role?)as the young Lord D'Ampton of D'Ampton Hall who must save the virgin sacrifice from the evils of... well, you'll just have to rent it.
Viewing hint: don't take it too seriously. Ken Russell didn't.
The song is an old traditonal. We've since found a few more verses.