The creature Gollum earned his name because of the horrible noises he makes in his throat. Gandalf the Grey speculated that he belonged to a race of river-folk akin to the hobbits, which once dwelt east of the Misty Mountains in the Vale of Anduin. Gollum’s tale is a sad and perilous one.
Sméagol, as was his name of old, went fishing on his birthday with his friend Déagol, who was suddenly pulled into the river by a fish. There, Déagol found a shiny gold ring in the silt at the river-bottom. Sméagol demanded the ring as a birthday present, but Déagol refused to relinquish it. Overcome by the power of the Ring – for this was the One Ring of the Dark Lord Sauron – Sméagol murdered his friend and claimed the Ring for himself. Banished by his people, he fled to a cave in the Misty Mountains, where the Ring’s power twisted his body and mind even as it prolonged his life for centuries.
Hundreds of years later, Gollum lost the Ring – or rather the Ring chose to be lost again – just in time for the hobbit Bilbo Baggins to stumble upon it. After a lengthy riddle-game in which Gollum tried to cheat his way to an easy meal – namely Bilbo – the hobbit escaped from the cave with the Ring’s aid, leaving the frustrated Gollum to stew in his own wrath until he at last gained the courage to leave the Misty Mountains in search of his birthday present. Since then he has endured many torments, including captivity at the hands of the Ranger Aragorn and the Elves of Mirkwood, and also torture in Mordor at the whim of Sauron. Still he endures, driven by a ceaseless yearning to regain the Ring… his “precious.” - Official Lorebook text.
Gollum can be found on landscape: