So, their origin is they used to be fey called pechs which got stuck in the Darklands and went insane. In DND they were a combination of humans and dwarves created from some experiment or something (I don't really remember.)
none, they're gnomes in pathfinder
You might be thinking of Duergar in Pathfinder. Duergar were Dwarves at one point, but they split up because Dwarves liked being under mountains and Duergar preferred to go as deep as possible, and the Duergar consider themselves to be the only true Dwarves. Even though Duergar are evil af, they're still honorbound like Dwarves are.