This question already has an answer here:
The corrupting effects of the One Ring on the hobbit Sméagol are well-known: when his relative Déagol found the Ring, Sméagol became instantly affected by its influence and strangled Déagol when he refused to hand over the Ring. The One Ring changed Sméagol into a grotesque creature that lived in the darkness and shadows of goblin tunnels and caves; and fed on stray goblins / fishes or basically whatever squiggly stuff that could be found. The ring also gave him unnaturally long life span and a personality like a crazy road lizard.
But how did Sméagol's name become Gollum? Why did people start to address him as Gollum? Was the name an inherent alter-ego that came with the ring? Did someone name him Gollum?