Like the other guy said, it seems to originate in Tarzan movies but it was co-opted by Black teens in Oakland during the 70s (I'm okay about being corrected here - earlier?) as a slang power-grunt.
I'd love to see someone provide additional words to my example. It's been a LONG time...
Foot-stomping chant (by late 70s it was used by cheerleaders and double-dutch):
Momma's got the powa
I said it, I meant it
I'm here to represent it
My back is achin', My belt's too tight
My hips are shakin' from left to right...
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