World-Shaking Bone Mag Uruk Salaka was known in Ork language as—Iron Skull. Mega Huge. Very Orky. The Boss of Real Bosses. Or, if those titles were too long for your liking, you could just call him Bonecrusher Salaka. Or simply Bone Uncle. He could carry the name.
His gun barrel was bigger than half a Space Marine's head. It was a Dreadnought. Bang!
Just like a certain Adeptus Custodes who did not wish to be named was privately called Kitty by his comrades.
Salaka's life had been legendary. His past was legendary, his present was legendary, and surely his future would carry that legend onward. Originally, he had been an ordinary Ork born in a mushroom pit on Uruk's little stone planet, living peacefully like every other Ork.
Chopping off the heads of neighboring Orks, or secretly knocking the big teeth out of their mouths with a hammer to buy some fungus brew—until they were attacked by the Imperium's army, and our legendary Bone Uncle had his head blown apart by a bullet, losing nearly all of his brain matter.
After the mad doc Grotsnik had worked his mystical magic to save him, sealing his skull with a chunk of Adamantium and stuffing the missing parts of his brain with a whole heap of bizarre discarded metal components, Uruk became Bone Uncle.
In his hallucinations, he saw visions of Gork and Mork. Those visions made him think harder and harder, and through all that thinking, he came to believe that he was the chosen Ork. From then on, whenever the mood took him, he called himself the prophet of Gork and Mork.
With such intensely devout thinking, Bone Uncle took only six short years to rise from a perfectly ordinary, skinny little Boy into the boss of the Goff Tribe.