"Fooler." The fetter with which the Æsir bound the giant wolf Fenrir. The two previous attempts to bind the wolf failed because those fetters — Lædingr and Drómi — proved no match for the wolf's enormous strength. The Alföðr then sent Freyr's messenger Skírnir down into the region of the black elves, to certain dwarfs, to have them make an unbreakable fetter. According to Snorri Sturluson in Gylfaginning, it was made from six things, namely "the noise a cat makes in foot-fall, the beard of a woman, the roots of a rock, the sinews of a bear, the breath of a fish, and the spittle of a bird." Gleipnir is described as "smooth and soft as a silken ribbon," but incredibly strong.
The Æsir showed Fenrir the fetter and said that it was much stronger than it looked. Each tested it with the strength of their hands and it did not snap; yet they said that the wolf could break it. Fenrir said to them:
Touching this matter of the ribbon, it seems to me that I shall get no glory of it, though I snap asunder so slender a band; but if it be made with cunning and wiles, then, though it seem little, that band shall never come upon my feet.
The Æsir answered that he could easily snap apart a light silken band, he who had before broken great fetters of iron, but if he should not be able to burst this band, then he would not be able to frighten the gods; and they would release him. The wolf agreed to be bound on the condition that, as a token of good faith, one of the gods laid his hand in Fenrir's mouth. Only Týr stepped forward. The wolf lashed out and immediately the fetter became hardened, and the more he struggled against it, the tighter the band was. Thus Fenrir was bound and all the gods laughed, except Týr: he lost his hand.
Gleipnir shall restrain Fenrir until the cataclysmic events of Ragnarök; then the wolf shall break his bond and devour Odin.
- Gylfaginning, 34.