I just linked to this old thread from a current one. But here goes...

As far as I know, Brown & Yellow "Earl" comes from American singer Debby McClatchy, who learned the song on one of her many trips to Britain (from the 70s, 80s or so). Her version was published in the Chicago folk music mag Come For To Sing, and did get some circulation in the US. She misheard the words; it's a mondegreen.