Coach slaps player's ass (especially wrestlers)

One time I was watching a football college game on TV. A University of Oklahoma player was on the ground. One of his teammates extended his hand to help him up. When the team mate was back up, the helping hand team mate gave that team mate a feel of his crotch with his open hand. I couldn't believe what I just saw on national TV. The receiving team mate didn't flinch or show any surprise. He just acted normal as if it was nothing.
 
One time I was watching a football college game on TV. A University of Oklahoma player was on the ground. One of his teammates extended his hand to help him up. When the team mate was back up, the helping hand team mate gave that team mate a feel of his crotch with his open hand. I couldn't believe what I just saw on national TV. The receiving team mate didn't flinch or show any surprise. He just acted normal as if it was nothing.
Hmmm... could it be that grabbing his junk was actually a way of expressing a teammate's support. I can imagine a society where men did that for each other, an intimate way of saying, I"m here for you." Of course, when I imagine such things, it usually involves more basic (i.e., "primitive") societies, probably because I read somewhere of an African tribe that goes naked and in which the mean greet each other by grasping each other's penis.
 
Sometimes find myself missing the good old days of scholastic and collegiate wresting when the coach and assistant coach would often slap the wrestler's asses, mine included, after a good match/meet
It seems like a lot of guys liked that acknowledgement from their coach or teammates, but the question is WHY? Why that particular gesture? Not a clap on the shoulder or a pat on the back. It was a slap on the ASS. Why?
 
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