Английский Этимологический словарь - swift (adj.)

- O.E. swift "moving quickly," related to swifan "move in a course, sweep" (see swivel). The bird (several species of the family Cypselidж, resembling swallows), noted for its "swift" flight, was so called from at least 1668. The name had earlier been given to several small fast lizards (1530).