I guess I'll give it a go.
Growing up, I loved to play cornerback. Most other kids wanted to be a receiver or a QB, I was basically the only one that actually enjoyed playing defense. Not tackling, mind you, but the one-on-one struggle between a WR trying to get the ball and a CB doing all he can to stop him. The only somewhat famous white CB during my childhood was Jason Sehorn (and I'm white as well or caucasian
if you want to make a big deal about it
), so my friends used to call me by his name.
I thought it would be a bit funny to spell it Sea
horn, and voila, you have my screenname.