Bilbo Baggins gives the name Sting to the sword he finds in the Trolls’ cave in The Hobbit.
Bilbo discovers Sting alongside two larger Elvish blades, Glamdring and Orcrist, after Gandalf, Thorin, and the company find the trolls’ hoard. Because the sword is small for a human or larger warrior, it suits a Hobbit particularly well.
Sting has a distinctive magical property: its blade glows blue when Orcs or other creatures called Goblins are nearby. Bilbo later uses it during his escape from the giant spiders of Mirkwood, where he names the weapon after stabbing one of them.
The sword also appears in The Lord of the Rings, where Bilbo gives it to Frodo. Sting is sometimes confused with Glamdring, Gandalf’s sword, or Orcrist, Thorin’s sword, but those are separate blades from the same ancient hoard.