sentences:  The swifts' nearest relatives are the New World hummingbirds and the Southeast Asian treeswifts.Its scientific name "Apus" is Latin for a swift, thought by the ancients to be a type of swallow with no feet (from Ancient Greek α, "a", "without", and πούς, "pous", "foot").Swifts have very short legs which they use primarily for clinging to vertical surfaces (hence the German name "Mauersegler", literally meaning "wall-glider").