The name of Thor's hammer is Mjöllnir, which means crusher or grinder. Eitri created it through a bet with Loki, who bet his head that Eitri, and his brother Brokkr, could not create anything as wonderful as the things the Sons of Ivaldi created. Though Loki tried to distract them by changing into a fly and repeatedly biting Brokkr, the two dwarfs succeeded in creating the magic arm ring Draupnir for Woden, the golden boar Gullinbursti for Freya, and the one handed hammer Mjöllnir for Thor.
Mjöllnir has become a symbol of righteousness, justice, and strength. As such it was adopted by Heathens and other Norse Reconstructionalists as a symbol of their faith.