It's the pop of the p in push that gives it the force. The sh is the sound of it shlooshing to a stop like someone silly enough to think that it's a neat idea to put on 30 lbs of equipment so that he won't know he's been hurt when someone 50 lbs heavier than he has popped him back.
Bolding deliberately left out. I couldn't be bothered.

Are you saying that "push" is exclusive to American sports?


The idiot also known as Capfka ...