late 14c., "the evening star," from Old French vespre "evening, nightfall" (12c., Modern French vêpre), from Latin vesper (masc.), vespera (fem.) "evening star, evening, west," 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." Meaning "evening" is attested from c. 1600.

Vespers "sixth canonical hour" is attested from 1610s, from plural of Latin vespera "evening;" the native name was evensong (Old English æfen-sang).

also north-west, Old English norþwest (adv.) "to a point or in a direction between north and west;"  from north + west. As a noun, "region or locality lying in the northwest of a country," and adjective from late 14c.

In U.S. geography it was at first, the territory that later became Ohio, Indiana, Illinois, Wisconsin, Michigan and northeastern Minnesota (1787); after about 1853 the term was applied to the unorganized territory north of Nebraska, west of Minnesota, and east of the Rockies. Pacific Northwest, describing Oregon and Washington, is by 1874. Related: Northwestern; northwesterly; northwestward (late 14c.).

Northwest Passage as the name of an at-first hypothetical sea route from the Atlantic to the Pacific by the northern coasts of North America, first attested c. 1600. The Northwest Ordinance (1787) was an act of Congress to organize the territory beyond the Appalachian Mountains between the Great Lakes and the Ohio River.

Old English suð-west; see south + west. As a noun from early 12c. Related: Southwester; southwesterly. The nautical coat called a sou'wester (1836) protects the wearer against severe weather, such as a gale out of the southwest.

Anglo-Saxon kingdom in southern England, literally "(land of the) West Saxons;" see west + Saxon. Modern use in reference to southwestern England (excluding Cornwall) is from Hardy's novels.

"to go west, travel westward," late 14c., from west (adv.), and compare westerly. Related: Westered; westering.

prevailing winds in certain latitudes, 1876, from westerly (see west).

"toward or of the west," late Old English westerne "western, westerly, coming from the west," from west + -erne, suffix denoting direction. The noun meaning "book or movie about the Old West" is first attested 1909. Westerner is from 1837 as "person from the U.S. West," 1880 as "Euro-American," as opposed to Oriental.

"toward the west," Old English westweard; see west + -ward.