Mine came from my motocross days in the early 1990's. I was riding this old, slow 1978 YZ125 dirtbike at a local practice track. One of the factory pros of the era was there and made a comment to one of my buddies that "The guy on that old bike sure is slick out there."
When I came off the track for a break my buddy said "You've got your nickname now. You're Slick."
Mx = motocross and Slick
I hope to return to racing again soon, and until I earn my standing I'll be running #50.
My cat's name is Gizmo.