OMG! I actually have a cousin named Cash! At least, I always thought that was his legal name. It wasn't until we got an invitation to his wedding that I found out his real name was Donald. The whole family had always called him Cash, never by any other name. When I asked why, they said it was because he was born in December and they could claim him as a tax deduction. Apparently, his dad started calling him Cash as a joke, but it stuck.
I have a cousin named Twig. I did find out his legal name when he got married, but I can't remember it now.