Interesting flow of "Whoo-YA"'s etymology.
I concur that its spelling on this thread as "WHOO-Ya!" comes directly and ONLY from KMET's 70's radio days. The use of "Hoo-Rah" and its various permutations is, indeed, a military origin.
Truth be told(and if it was already stated here, sorry, I just didn't see it referenced...) "Whoo-Ya!" as KMET intended it had nothing to do with triumphant exclamation. It referred to dopers, hopheads, and stoners who smoked paraquat-infested marijuana. The defoliant clearly did nothing to deter pot smoking, but resulted in a sound like cardboard tearing at every concert in Los Angeles that I attended. My older brother attended Cal Jam 1 and 2, and claimed that the only thing more persistent than the bad sound system was the gravely hacking of paraquat-spewing, red-eyed hippies who refused to give up the leaf. "WHOO-Ya!" perfectly mimics what that sounded like, even in my distant memories.
Anyway, just my two cents. Great forum here, folks.
Fin