Which Tolkien character was originally named Sméagol?

The Tolkien character originally named Sméagol is Gollum.

Sméagol was a Stoor, a Hobbit-like people, before the One Ring transformed his life. He obtained the Ring after killing his relative Déagol, who had found it while fishing in the Gladden Fields. The Ring’s influence isolated and corrupted him over centuries.

He became known as Gollum because of the unusual gurgling sound he made. Tolkien presents Sméagol and Gollum as connected aspects of one damaged personality, rather than as two unrelated characters. In The Hobbit, Gollum lives beneath the Misty Mountains and challenges Bilbo with a riddle game.