Fenrir was growing at an alarming rate, and the gods knew how much devastation he would cause if he were allowed to roam free, the gods attempted to bind him with various chains. They were able to gain the wolf’s consent by telling him that these fetters were tests of his strength, and clapping and cheering when, with each new chain they presented him, he broke free.
When the gods presented Fenrir with the chain Gleipnir, the wolf suspected trickery and refused to be bound with it unless one of the gods would lay his or her hand in his jaws as a pledge of good faith. None of the gods agreed, knowing that this would mean the loss of a hand and the breaking of an oath. At last, the brave Tyr, for the good of all life, volunteered to fulfill the wolf’s demand. And, sure enough, when Fenrir discovered that he was unable to escape from Gleipnir, he chomped off and swallowed Tyr’s hand.