Gollum’s name before he becomes known as Gollum is Sméagol.
Sméagol is a member of the Stoor branch of hobbits. He discovers the One Ring after Déagol finds it while fishing in the Gladden Fields. Sméagol murders Déagol to take the Ring, and the Ring’s influence contributes to his long transformation into the isolated creature later called Gollum.
He hides beneath the Misty Mountains for centuries, living on raw food and maintaining a conflicted relationship with the Ring. Tolkien’s narrative presents both Sméagol and Gollum as aspects of the same character, showing how possession and corruption divide his identity.
Déagol is often confused with Sméagol because the two appear together in the Ring’s discovery story. Déagol finds the Ring; Sméagol takes it and becomes its first known hobbit owner.