Gollum was a Stoor Hobbit of the River-folk who lived near the Gladden Fields. In The Lord of the Rings it is stated that he was originally known as Sméagol, corrupted by the One Ring, and later named Gollum after his habit of making “a horrible swallowing noise in his throat”.
How did Sméagol become Gollum?
Living underground without contact with anyone or without sunlight, Sméagol became sickly. He would produce a gurgling cough almost like he was choking. The sound of the cough was what led to him being known as Gollum.