One of the neighborhood guys that we used to play pick up ball with was getting ticked off at me that an extremely skinny kid 4 years his junior was making every shot out there, and consequently rejecting most of his...and he just blurted out...."Take it easy Manute you're killin me!".
I wasn't that tall back then, but as skinny as I was, I could jump very high. Everyone had a good laugh with it and the nickname stuck all through middle and high school.