Gray-rumped treeswift 
(Yến mào phao câu xám, Hemiprocne longipennis)

The grey-rumped treeswift (Hemiprocne longipennis) is a species of bird in the Hemiprocnidae family.
The bird is found in Brunei, Indonesia, Malaysia, Myanmar, the Philippines, Singapore, and Thailand.

Hemiprocne: Greek hemi- half-, small, akin to; Latin progne: swallow.
Longipennis is a New Latin adjective meaning "having long wings". 
The term comes from the Latin words longus (long) and pennis (wings).