"life of idle begging," 1706, from vagrant + abstract noun suffix -cy. Earlier in a figurative sense, "mental wandering" (1640s). By late 18c. used in law as a catch-all for miscellaneous petty offenses against public order.

early 15c., from Anglo-French vagarant, waucrant, and sharing with it the history to be found under vagrant (n.). Dogberry's corruption vagrom ("Much Ado about Nothing") persisted through 19c. in learned jocularity.

mid-15c., "person who lacks regular employment, one without fixed abode, a tramp," probably from Anglo-French vageraunt, also wacrant, walcrant, which is said in many sources to be a noun use of the past participle of Old French walcrer "to wander," from Frankish (Germanic) *walken, from the same source as Old Norse valka "wander" and English walk (v.).

Under this theory the word was influenced by Old French vagant, vagaunt "wandering," from Latin vagantem (nominative vagans), past participle of vagari "to wander, stroll about" (see vagary). But on another theory the Anglo-French word ultimately is from Old French vagant, with an unetymological -r-. Middle English also had vagaunt "wandering, without fixed abode" (late 14c.), from Old French vagant.

plural vagi, 1840, "pneumogastric nerve," the long, widely distributed nerve from the brain to the upper body, from Latin vagus "wandering, straying" (see vague).

"uncertain as to specifics," 1540s, from French vague "empty, vacant; wild, uncultivated; wandering" (13c.), from Latin vagus "strolling, wandering, rambling," figuratively "vacillating, uncertain," perhaps from PIE *Huog-o-  and cognate with Old Norse vakka "to stray, hover," Old High German wankon "to totter, stagger," Old High German winkan "to waver, stagger, wink," Old English wincian "to nod" [de Vaan]. Related: Vagueness.

1748, from vague + -ly (2).

"advantage, profit," early 15c., from vail (v.) "to be of use or service" (c. 1300), from Old French vail, from valoir "to be of value or worth" (see value (n.)).

c. 1300, "devoid of real value, idle, unprofitable," from Old French vain, vein "worthless, void, invalid, feeble; conceited" (12c.), from Latin vanus "empty, void," figuratively "idle, fruitless," from PIE *wano-, suffixed form of root *eue- "to leave, abandon, give out."

Meaning "conceited, elated with a high opinion of oneself" first recorded 1690s in English; earlier "silly, idle, foolish" (late 14c.). Phrase in vain "to no effect" (c. 1300, after Latin in vanum) preserves the original sense. Related: Vainly; vainness. Compare also vainglory.

c. 1200, "worthless glory, undue pomp or show," waynglori, from Old French vaine glorie, from Medieval Latin vana gloria (see vain + glory (n.)).

early 15c., from vainglory + -ous, or from Old French vain glorios "boastful, swaggering." Related: Vaingloriously; vaingloriousness. Grose ("Classical Dictionary of the Vulgar Tongue," 3rd ed., 1796) has vain-glorious man "One who boasts without reason, or, as the canters say, pisses more than he drinks."