What is "chrestomanci"

Chrestomanci, sometimes branded The Worlds of Chrestomanci, is a series of seven children's fantasy books by the British author Diana Wynne Jones, published from 1977 to 2006. In the context of the parallel universe setting of the books, Chrestomanci also refers to the eponymous British government office that is responsible for supervising the use of magic and Chrestomanci Castle in southern England , which is both residence and headquarters.

The word "Chrestomanci" may be derived from the Greek khrestos, meaning "useful", and -mancy, "divination". In turn -mancy is derived from Ancient Greek manteía, " prophecy or divination". Jones gives the pronunciation "KREST–OH–MAN–SEE" herself and one of her characters writes the same instruction for using the word as a spell.