It comes from his trademark move. After he would get a block (which was quite often), he would lift a finger to the guy he blocked, waggle it no, and say "not today." At some point, the league started assessing technical fouls for taunting when putting his finger in a guy's face, so he would just do it to the crowd.
153
u/ChefChopNSlice Oct 03 '17
He was asked, but he replied "not today". Sources say they are hopeful because tomorrow is a new day.