Gollum

Gollum was a name used by Rose Tyler to refer to Chip, the servant of Lady Cassandra O'Brien.Δ17. (TV: New Earth)

Clyde Langer called Commander Kaagh Gollum. (PROSE: The Last Sontaran)

Behind the scenes
In the real world, Gollum is a character from The Lord of the Rings by J. R. R. Tolkien. Televised Doctor Who never explicitly makes this connection.