Once known as Big Lugg, he was raiding a Dwarf brewery with his greenskin mates when he was hit in the face with a stone from a Grudge Thrower. It failed to kill him, although it did remove what little wits he had. When the giant woke up he was convince that he was the greenskin god Gork. 
He smeared his hands and feet with green paint, and now delights in jumping up and down on any non-greenskin that gets in his way, shouting Waaagh! at the top of his lungs.