means A small, sickle-winged bird that spends almost its entire life on the wing, named for its remarkable speed in flight; more broadly, 'swift' means moving or happening with great quickness.

from From Old English 'swift,' meaning fast or quick, tied to the verb 'swīfan,' to move in a sweeping path or revolve — a fitting root for a creature whose whole existence is one ceaseless sweep through the air. The adjective came first; the bird borrowed it, earning the name by living up to it.