Gollum’s original name in J.R.R. Tolkien’s fiction was Sméagol.
Sméagol belonged to a river-dwelling people related to the Hobbits. On his birthday, he went fishing with his relative Déagol, who discovered the One Ring in the River Anduin. Sméagol wanted the Ring and murdered Déagol to take it, beginning his long corruption.
The Ring’s influence and Sméagol’s isolation gradually transformed him. He eventually lived beneath the Misty Mountains, where he became known as Gollum because of the choking, gurgling sound he made. Tolkien presents Gollum as a divided figure, with remnants of Sméagol still struggling against the Ring’s domination.
Déagol is sometimes mistaken for Gollum’s original identity, but Déagol was the companion who found the Ring. Sméagol is also distinct from Smeagol’s modern spelling without an accent; Tolkien’s name is commonly written Sméagol in English editions.