The Collaborative International Dictionary of English v.0.48:
Hobby \Hob"by\, n.; pl. Hobbies. [OE. hobi; cf. OF. hobe, hob['e], F. hobereau a hobby, a species of falcon. OF. hober to move, stir. Cf. Hobby a horse.] (Zool.) A small, strong-winged European falcon (Falco subbuteo), formerly trained for hawking. Hobby