Origin and history of vesper

late 14c., "the evening star, the planet Venus seen at evening," from Old French vespre "evening, nightfall" (12c., Modern French vêpre), from Latin vesper (masc.), vespera (fem.) "evening star; evening;" poetically, "the west."

It is related to Greek hesperos, and ultimately from PIE *uekero- "evening, night" (source also of Armenian gišer, Old Church Slavonic večeru, Polish wieczór, Russian večer, Lithuanian vākaras, Welsh ucher, Old Irish fescor "evening"), perhaps an enlarged form of root *we- "down" (source of Sanskrit avah "down, downward"), thus literally "direction in which the sun sets."

The meaning "evening" is attested in English from c. 1600. The vesper-bird (1821 in general, by 1874 as a specific bird) often sings as night shadows fall.