Aithusa is a white dragon summoned by Merlin. On the show the name is said to mean "light of the sun" in Ancient Greek, but this is incorrect. Aithusa is the name of a portico or veranda built with an open ceiling in order to bring in light. The writers of the show may have confused the purpose of an aethusa to be its meaning. -behindthename.com/name/aithusa/submitted.