Somewhere in the back recesses of my mind-housing-group I expected that it might be an outgrowth of the old, 1956 flik, THE DI, starring Jack Webb as Gunny Moore, where he commands his recruit platoon, "Tigers, Let Me Hear You ROAAAARRR!!!"
It wasn't all that many years after that when the oohrah thing began.
But it now seems that that is a much too simple an explanation for anyone to accept.
Dick Gaines