I've been and avid reader, a lover of poetry and a devotee of folklore for a long time, and my ear tells me that this song is so slick, so enigmatic, so careful to avoid commitment to any kind of meaning, that it is a hoax. I suspect it was written in the late 19th century, either as a parody of folksongs or just because somebody had come up with a good tune and wanted some words for it. And, in the final analysis, what's wrong with that?