Scholars believe that he was the original chief god, the Germanic equivalent of the Greek Zeus, who was later overtaken in popularity and therefore in authority by Odin. He was known for his courage: at one stage the gods decided to shackle the wolf Fenrir, but the beast broke every chain they put upon him. Eventually they had the dwarfs make them a magical ribbon (Gleipnir) from such items as a woman's beard and a mountain's roots. But Fenrir sensed the gods' deceit and refused to be bound with it unless one of them put his hand in the wolf's mouth. This, we are told, is how Fenrir was bound until the day of Ragnarok and how Tyr lost his hand.
Tuesday is named for Tyr (in Old English, Tiw).
Alternative: Tiw (Old English), Ziu, TÓwaz