What's the name of Thor's hammer?

When Marvel Comics introduced Thor in 1962, they equipped him with his trusty hammer Mjolnir. The whole "whosoever holds this hammer, if he be worthy" thing is purely Marvel's invention. In Norse mythology, the hammer was just really heavy and super powerful, and even Thor needed special iron gloves just to use it properly. Stan Lee and Jack Kirby kept the dwarves as the makers of the hammer, but the original myths never specified what magical metal they used to forge it.