Gleipnir (Old Norse 'open one', 'lissom') is the name of the fetter with which the wolf Fenrir can finally be bound. Skírnir fetched it for the Æsir from the dwarfs who had made it
The fetter is extremely light and soft but Fenrir cannot break it. [1] [2]
Gleipnir is also used as an Icelandic horse name