Gull-billed tern 
(Nhàn chân đen, Gelochelidon nilotica), formerly Sterna nilotica
formerly placed in the genus Sterna.

The gull-billed tern (Gelochelidon nilotica) is a tern in the family Laridae. 
The bird is widely distributed and breeds in scattered localities in Europe, Asia, northwest Africa, and the Americas.

Charadriiformes, Charadriidae, Charadrius: Late Latin word for a yellowish bird mentioned in the fourth-century Vulgate; from Ancient Greek kharadrios a bird found in ravines and river valleys (kharadra, "ravine").

Laridae:from Ancient Greek laros or Latin larus, which appears to have referred to a gull or other large seabird.

The genus name Gelochelidon combines the Ancient Greek gelao meaning "to laugh" with khelidon meaning "swallow".

The specific epithet nilotica is from Latin niloticus meaning "of the River Nile".