Pop Goes the Weasel

I've had this conversation with a few other moms. Nursery rhymes really are bizarre. Pop goes the weasel? What does that even mean? It's fun to sing, but how does a weasel go pop? Why would Ms. Muffet sit on a tuffet? What about Humpty Dumpty? Nothing wrong with a little silliness, especially if our little guy likes it...