Character names in her books are often clues to their identities or secrets. For example, Professor Remus Lupin is a werewolf. According to myth, Romulus and Remus were the founders of Rome and were raised by wolves. His last name, Lupin, is derived from the Latin lupus, for wolf, and the English adjective lupine, meaning wolf-like. Lupin was converted into a werewolf by Fenrir Greyback, whose name is taken from Fenrir, the monstrous wolf son of Loki in Norse mythology. (His alias, Fenrisulfr, was the basis for Fenris Ulf, the American name for Maugrim in C.S. Lewis's "Chronciles of Narnia".) Sirius Black, who turns into a black dog, is named for the star Sirius, which can be found in the constellation Canis Major - the big dog.