The bird genus Apus comprise some of the Old World members of the family Apodidae, commonly known as swifts.
The name Apus is Latin for a swift, thought to be a type of swallow with no feet (from Ancient Greek a meaning "without", and pous meaning "foot").

1/ Little swift (Yến cằm trắng, Apus affinis)

2/ Pacific swift or fork-tailed swift (Yến hông trắng, Apus pacificus)
pacificus refers to the Pacific Ocean.