Gob was a brute of a dwarf, burly, tall and unbelievably strong. And undeniably stupid.
No one really knew where Gob came from or who he was, but everyone agreed that he was essentially a mighty, big oaf. He spent days entertaining fellow dwarfs at his own expense, until one of the many pranks played on him went too far. Confused and cornered, Gob lashed out and, using his retard strength, strangled a dwarf who was too zealous with the "gob-beating stick". Deemed an unworthy offering to Armok he was sent off to a crazy project called Steelhold. A penal colony.
Arrival and glory
Later that year, he took part in the escalation of Steelhold-Goblin War, bashing everything in his way into a bloody pulp. Notably, he went straight for the goblin warlord, as if guided by some sort of animalistic intuition, which helped immensely in repealing siege without further losses.
He was granted a first killing strike in The Dented Attack, felling no one else than Atu the goblin master himself. But, as stupid as he was, Gob forgot that in his charge, he ran straight into a platoon of enraged goblins... Thus, he became the first victim of traitorous Stozu Monsterenjoyed, who got clear shot on a dwarf overwhelmed by her comrades.
Gob had a bare minimum of feelings and brains to develop a complex persona. Mostly he lived in a white-black world, beating up everything he didn't like. There always was someone to tell him, who exactly he didn't like so much.
Gob became a common word to describe someone stupid, yet utterly zealous and surprisingly effective. It has some correlation with "gobs", short for "goblins", but is used in a more positive way. For example, dwarves could say about goblin who stupidly went on a nearby titan/dragon/whatever enemy of a fortress there was, ignoring all other targets, as being true Gob