The words and melodies of traditional songs have been written down by all sorts of people over several hundred years; interest in such things is by no means a new phenomenon.  The subject is too large to go into in any depth here, but as you learn more you'll find out all sorts of stuff, and the Mudcat is a good place to start.  Once you're familiar with the extremely useful "Digitrad and Forum Search" facility on the main Forum page, you'll be able to waste whole days looking things up!

On the subject of The Cruel Sister and its many variants and relatives, I've put a list of links to material available here and elsewhere in this recent discussion:

lay the bent to bonny broom

Malcolm