Elemental Celerity is a job trait from Final Fantasy XI. It can be obtained by Black Mages at Level 50 and Geomancers at Level 55. Unlike Fast Cast, Elemental Celerity only reduces the casting time of elemental magic spells.
Classical elements typically refer to ancient concepts similar to the modern states of matter: earth (solid), water (liquid), air (gas) and fire (plasma). Classical elements are the simplest form of existence, of everything in existence. Many philosophies and worldviews believe in classical elements.
Celerity is an archaic noun that means "swiftness" or "speed".