Gogmagog (also Goemagot, Goemagog, Goëmagot and Gogmagoc) was a legendary giant in Welsh and later English folklore. According to Geoffrey of Monmouth’s Historia Regum Britanniae (“The History of The Kings of Britain”, 12th century), he was a giant inhabitant of Albion, thrown off a cliff during a wrestling match with Corineus (a companion of Brutus of Troy). Gogmagog was the last of the Giants found by Brutus and his men inhabiting the land of Albion.
The effigies of Gogmagog and Corineus, used in English pageantry and later instituted as guardian statues at Guildhall in London eventually earned the familiar names “Gog and Magog”.
Source: Gogmagog (giant) – Wikipedia