Galligantus

Galligantus, or Galligantua, was one of the giants in the fable of Jack the Giant-Killer. The name may have been inspired by Gargantua.

According to Brewer’s Dictionary of Phrase and Fable, Galligantus lived with Hocus-Pocus in an enchanted castle. By his magic he changed men and women into dumb animals, amongst which was a duke’s daughter, changed into a roe. Jack the Giant Killer, arrayed in his cap, which rendered him invisible, went to the castle and read the inscription: “Whoever can this trumpet blow, will cause the giant’s overthrow.” He seized the trumpet, blew a loud blast, the castle fell down, Jack slew the giant, and was married soon after to the duke’s daughter, whom he had rescued from the giant’s castle.

In other versions of the tale, the giant's head is sent to King Arthur.