Tree of mine, tree of mine,
Have you seen a girl
With a willy-willy wag, and a long-tailed bag,
Who's stole my money, all I had?'
This is from an English fairy tale "The Old Witch". This was said by a witch, when she run after a girl who stole a great bag of money of her and arrived at a tree which a girl hid behind. What's the meaning of "a willy-willy wag"?