Trolls were creatures from Earth myths and legends. Trolls existed in the Land of Fiction. Some of them were converted into Cybermen. (AUDIO: Legend of the Cybermen) The Fomoir of Tír na n-Óg resembled trolls by design. (PROSE: Cat's Cradle: Witch Mark) The name was also used as an insult; Susan Foreman called the Master a troll. (PROSE: Legacy of the Daleks)
When the Tenth Doctor engaged contact with General Staal during the Sontaran invasion of Earth, UNIT Colonel Alan Mace likened the appearance of the Sontaran to that of a troll. (TV: The Poison Sky)
Trolls also formed the basis for a popular brand of toys on Earth. When she was a child, Jo Grant had "an army of gonks and trolls" but even then found dolls creepy. (AUDIO: The Doll of Death)