Origin of the Booyaka ~
"Mira, the barbarian queen, was the most beautiful woman who ever lived. She and her husband, the mighty Trinder, ruled their tribe in harmony for many years. Everybody thought they rocked. There was plenty of food and life was good.
One day the malicious
half-god, Malth, happened upon Mira in the forest, who was there
collecting berries and flowers and all. He silently watched Mira from
behind a tree, and was quickly consumed by lust for her. He took the
shape of a wild rabbit, and hopped over to where she was foraging.
Because of his harmless appearance, Malth was able to trick her into
eating a special mushroom which sent her into a licentious trance, and
he had his way with her.
Through the vile union between Mira and the spirit-beast, she conceived two children. Giving birth to the children would claim her life, though the tribal shamans tried to save her by dancing their dances and working their juju. Trinder, though once a great warrior, could not bear Mira's death, and so he took his own life on the cliffs. You can bet everyone was pretty bummed out, after all that.
The
two children were taken in and raised with love by the tribe - a
tribute to the queen they adored. Both of them, one boy and one girl,
grew very strong because the blood of a spirit-beast ran through them.
Even as children, they could run, jump, and fight better than anyone
else in the village.
Rahm, the boy, was exceedingly strong, and had
become a very powerful warrior by the time he was a young man. His
sister Mara, who was equally strong, excelled in the smithing of
weapons, and the teachings of the shamans. When they were old enough,
they learned the nature of their sweet mother's death, 
and the young warriors resolved to claim retribution. They sought to find their father Malth, and kill him.
The clan elders advised that killing a half-god would be no simple
task. To accomplish this, they told Rahm and Mara, they'd need a
kickass magical weapon, because any old regular one wouldn't work. So,
while Rahm trained with his masters and honed his strength, Mara
labored to create a colossal mallet, to be her brother's weapon in
battle. She entwined powerful magics into the instrument, and stained
the wooden handle with her own spectral blood in the full-moonlight. At
last, Rahm retrieved their mother's skull from its tomb, and it was
cast in molten iron and set steadily atop the hulking cudgel, to serve
as the weapon's head.
When the final spells had been cast and the
weapon was complete, the elders all agreed that it was perfect - the
finest craftwork the mountain folk had ever yielded. So it was that the
legendary weapon Bonesnap came to be.
The next dawn, Rahm prepared for battle, and trekked far out to
the cave where Malth dwelt. He entered, and came at last to a vast
cavern where, among myriad piles of gems and gold, Malth laid sleeping
on a heap of exotic fabric and furs. His form was that of a huge
hare-beast, for while he slept he could not control his appearance,
thus revealing his true shape. Rahm roared with fury and went forth to
butcher the monster.
Awakened by the young barbarian's shout, Malth
rose quickly and gazed at Rahm. He recognized the barbarian at once and
saw his intent. Old Malth growled, cursed, and spit with hatred, mostly
because his bastard son had come to kill him, and partly because he
hadn't any coffee yet.
The spirit-beast
conjured fiendish missiles of ice and flame to do away with his son,
but the incantations that Mara had weaved into her brother's weapon
surrounded him with a protective glow, so Malth's sorcery could not
harm him.
With tremendous strength Rahm lept, high into the air,
and heaved the great maul aloft. He soared down on top of Malth, and
drove the hammer into the back of the creature's wretched neck. The
beast fell hence crushed and dead.
Rahm returned to his village at
sunset, shouldering his mighty hammer, with the bloody head of the
giant rabbit in hand. The villagers cheered "That is so awesome!" and he and his sister were soon married. ...to like, other people, not each other. They each had many children and reigned in peace 
for years to come.
So it came to pass that the tribe of the Booyaka, instilled with the ancestral spirit blood of Rahm and Mara, were endowed with might and the uncanny ability to leap great distances. When war would call them down from the mountains to the battlefield, the banners they bore were painted with the cleaved head of a hare."
- taken from an untitled tome discovered in a cave near Entsteig, year 1243.
* * *
...it seems that at some point, the common word Ka, described in Glynnath Cain's "A Brief History of Sanctuary I-X" as "the energy of all things", was combined with the barbarian phrase Bo-oya, which means roughly "to lay the smack down, like with a hammer". The two terms meshed to create the new expression Boo-ya-Ka, and was hence often shouted in conjunction with the killing blow of the tribe's unorthodox fighting style, fundamentally asserting, "I strike at you with the energy of all things" or also, "In your face, you sniveling milksop."
Such confidence was not unwarranted. So feared on the battlefield were they that entire battalions had been known to retreat at merely the sound of the Booyaka's approaching chants...
...The strange combat method of the Booyaka consisted mainly of springing high into the air while hefting a very heavy object and landing, violently, on top of their opponents. It was once thought that this super-human ability to hurl themselves skyward so effectively had come about because the tribe's native terrain was so demanding - the cliffs and valleys between the Gulf of Westmarch and Mt. Arreat were certainly rugged. The tribe's lore, however, offered a much more compelling explanation...
...As I recall, the story centered around the strange creation of an astonishing weapon..."
- exerpts from The Khanduras Memoirs