subs. (old).See quots.
1785. GROSE, A Classical Dictionary of the Vulgar Tongue, s.v. A monster with six eyes, three mouths, four arms, eight legs, five on one side and three on the other, three arses, two tarses, and a cunt upon its back; a man on horseback with a woman behind him.
1892. FENNELL, Stanford Dictionary, s.v. GORMAGON. a member of an English Secret Society which existed in the second quarter of 18 c.