Ever see the Tongan War Dances? Like before a rugby game? Or before starting battle?
The Indians did it, the Irish and the Scot did it, the Persians and their enemies the Greeks did it.
You stomp ground, pound the rear end of your weapon into the ground, you jump and pose, your roar and scream, THEN you're ready for battle.
Heck, even civilized nations did it, like the Japanese and the Chinese ..
, all the Pacific Islanders, the Incas and the Mayans.