Okay it was a old high school saying. Skinny chicks have no meat on there bones so when you are doing the deed the pelvis bones or what ever they are called rubs because there is not enough meat there hints you will skin up your dick,like road rash. Sorry guess ya had to be there, Or your not big enough to experence it.(BURN) . and Yes I have plenty of experence with both skinny and full body women.