The character later known as Gollum was originally named Sméagol.
Sméagol belongs to a river-dwelling people related to Hobbits. On his birthday, he and his cousin Déagol find the One Ring in the River Anduin. Sméagol desires the Ring immediately, kills Déagol to obtain it, and is eventually driven from his community because of his behavior.
The Ring’s influence helps transform Sméagol physically and psychologically. He hides beneath the Misty Mountains for centuries, where he becomes the creature called Gollum. The name reflects his distinctive choking or swallowing sound, which Tolkien uses as part of the character’s memorable speech and identity.
Gollum’s earlier life matters because Tolkien presents him as both a dangerous enemy and a tragic former person. His divided relationship with the Ring and with his “precious” helps shape the plot of The Hobbit and The Lord of the Rings.