I read as a child a children's book called The Nine Questions. At the end of it, the boy had to sing the replies to this song (with the questions being sung by the Minister Of Light.) He is able to answer the questions correctly because of the experiences he had in the previous chapters. Anyone else remember that book?

By the way, in the book's version of the song, there is no mention of the weaver until the final refrain, when the defeated devil tells him, "You are the weaver's barney!" It becomes clear in context that a barney is a ward or child.