It's a traditional song, not a carol exactly as it's nothing to do with Xmas. It gets sung (murdered, more like) at larp events (and no doubt folk events and all kinds of others). There are loads of verses kicking around, I picked a few that worked for me and change a few odds and ends (for eg it mentions October and that's not a DA name of the month so I altered the rhyme and the verse to fit better).

I've found you a version that is close to the tune in my head. http://www.youtube.com/watch?v=e7PYhCkNZh8