Bilbo gives the sword he finds in the trolls’ hoard the name Sting.
In The Hobbit, Bilbo, Gandalf, and the dwarves discover three ancient Elvish swords in the trolls’ cave. Gandalf takes Glamdring, Thorin takes Orcrist, and Bilbo initially chooses a smaller blade. Because it is short by the standards of the others, Bilbo names it Sting.
Sting later becomes one of Bilbo’s most important possessions. Its blade glows blue when Orcs or other nearby enemies are present, a property shared by the ancient weapons from Gondolin. Bilbo uses it during the escape from the goblins and against giant spiders in Mirkwood.
Bilbo eventually gives Sting to Frodo before Frodo leaves the Shire. Frodo carries it through much of The Lord of the Rings, including the journey into Mordor. Glamdring and Orcrist are separate swords, while Andúril is Aragorn’s reforged sword, so these names are not interchangeable.