Norse accents would be the closest to the mythical inspiration, but most people don't know what a Viking would have actually sounded like. Why Germanic accents and culture is rarely used for dwarves I'm less certain about, as there is a lot of cultural overlap there, and Dwarven tendency towards lawfulness could fit with the stereotype of German efficiency. But Scotsmen and Vikings certainly get associated with each other in popular consciousness, even if it was mostly in the form of a state of war IRL. Scottish accents are distinctive, thick, and aggressive, and associated with hairy, hard-drinking, hard fighting men who live in a clan structure.