Sixcat is my nickname, although most people don't call me that anymore since I don't live where I grew up. Some friends and I were playing basketball at the YMCA in my hometown when I was about 12 or 13 and we were destroying a team of older kids who were all JV players at the high school. Some of the coaches from the high school were there and one of those kids made a comment to a coach that "that cat can play some ball". I happened to be wearing a jersey of some sort (Kentucky, I think) with the number 6 on the back.
It stuck.
It stuck.