Online Etymology Dictionary

V: In Middle English, -u- and -v- were used interchangeably, though with a preference for v- as the initial letter (vnder, vain, etc.) and -u- elsewhere (full, euer, etc.). The distinction into consonant and vowel identities was established in English by 1630, under influence of continental printers, but into 19c. some dictionaries and other catalogues continued to list -u- and -v- words as a single series.

No native Anglo-Saxon words begin in v- except those (vane, vat, vixen) altered by the southwestern England habit of replacing initial f- with v- (and initial s- with z-). Confusion of -v- and -w- also was a characteristic of 16c. Cockney accents.

As a Roman numeral, "five." In German rocket weapons systems of World War II, it stood for Vergeltungswaffe "reprisal weapon." V-eight as a type of motor engine is recorded from 1929 (V-engine is attested from 1909), so called for the arrangement. The V for "victory" hand sign was conceived January 1941 by Belgian politician and resistance leader Victor de Laveleye, to signify French victoire and Flemish vrijheid ("freedom"). It was broadcast into Europe by Radio België/Radio Belgique and popularized by the BBC by June 1941, from which time it became a universal allied gesture.
V.D. (n.): 1920, short for venereal disease (see venereal).
v.i.: abbreviation of Latin vide infra, literally "see below."
vac: 1709 as a colloquial shortening of vacation (n.); 1942 as a colloquial shortening of vacuum (v.); 1974 as a colloquial shortening of vacuum cleaner.
vacancy (n.): 1570s, "a vacating;" c. 1600, "state of being vacant," from Late Latin vacantia, from Latin vacans "empty, unoccupied," present participle of vacare "be empty" (see vain). From 1690s as "a vacant office or post;" meaning "available room at a hotel" is recorded from 1953. Related: Vacance (1530s); vacancies.
vacant (adj.): c. 1300, "not filled, held, or occupied," from Old French vacant "idle, unoccupied" (of an office, etc.), from Latin vacantem (nominative vacans), "empty, unoccupied," present participle of vacare "to be empty" (see vain). Meaning "characterized by absence of mental occupation" is from 1570s. Related: Vacantly.
vacate (v.): 1640s, "to make void, to annul," from Latin vacatus, past participle of vacare "be empty, be void" (see vain). Meaning "to leave, give up, quit" (a place) is attested from 1791. Related: Vacated; vacating.
vacation (n.): late 14c., "freedom from obligations, leisure, release" (from some activity or occupation), from Old French vacacion "vacancy, vacant position" (14c.) and directly from Latin vacationem (nominative vacatio) "leisure, freedom, exemption, a being free from duty, immunity earned by service," noun of state from past participle stem of vacare "be empty, free, or at leisure" (see vain).

Meanings "state of being unoccupied," "process of vacating" in English are early 15c. Meaning "formal suspension of activity, time in which there is an intermission of usual employment" (in reference to schools, courts, etc.) is recorded from mid-15c. As the U.S. equivalent of what in Britain is called a holiday, it is attested from 1878.
vacation (v.): 1866, from vacation (n.). Related: Vacationed; vacationing.
vaccinate (v.): 1803, "to inoculate with a vaccine," originally with cowpox for the purpose of procuring immunity from smallpox, back-formation from vaccination. Related: Vaccinated; vaccinating.
vaccination (n.): 1800, used by British physician Edward Jenner (1749-1823) for the technique he devised of preventing smallpox by injecting people with the cowpox virus (variolae vaccinae), from vaccine (adj.) "pertaining to cows, from cows" (1798), from Latin vaccinus "from cows," from vacca "cow" (Latin bos "cow" being originally "ox," "a loan word from a rural dialect" according to Buck, who cites Umbrian bue). "The use of the term for diseases other than smallpox is due to Pasteur" [OED].
vaccine (n.): "matter used in vaccination," 1846, from French vaccin, noun use of adjective, from Latin vaccina, fem. of vaccinus "pertaining to a cow" (see vaccination). Related: Vaccinal; vaccinic.
vacillate (v.): 1590s, "to sway unsteadily," from Latin vacillatus, past participle of vacillare "sway to and fro; hesitate" (see vacillation). Meaning "to waver between two opinions or courses" is recorded from 1620s. Related: Vacillated; vacillates; vacillating.
vacillation (n.): c. 1400, "hesitation, uncertainty," from Latin vacillationem (nominative vacillatio) "a reeling, wavering," noun of action from past participle stem of vacillare "sway to and fro, waver, hesitate, be untrustworthy," of uncertain origin. Originally in reference to opinion or conduct; literal sense is recorded from 1630s.
vacuity (n.): late 14c., "hollow space," from Latin vacuitas "empty space, emptiness, absence, vacancy, freedom," from vacuus "empty" (see vacuum (n.)). Originally in anatomy. Meaning "vacancy of mind or thought" is attested from 1590s.
vacuole (n.): "small cavity or vesicle," 1853, from French vacuole, from Medieval Latin vacuola, formed as a diminutive of Latin vacuus "empty" (see vacuum (n.)).
vacuous (adj.): 1640s, "empty" (implied in vacuousness), from Latin vacuus "empty, void, free" (see vacuum (n.)). Figurative sense of "empty of ideas, without intelligent expression" is from 1848. Related: Vacuously.
vacuum (n.): 1540s, "emptiness of space," from Latin vacuum "an empty space, vacant place, a void," noun use of neuter of vacuus "empty, unoccupied, devoid of," figuratively "free, unoccupied," related to vacare "be empty" (see vain). Properly a loan-translation of Greek kenon, literally "that which is empty." Meaning "a space emptied of air" is attested from 1650s. Vacuum tube "glass thermionic device" is attested from 1859. Vacuum cleaner is from 1903; shortened form vacuum (n.) first recorded 1910.
The metaphysicians of Elea, Parmenides and Melissus, started the notion that a vacuum was impossible, and this became a favorite doctrine with Aristotle. All the scholastics upheld the maxim that "nature abhors a vacuum." [Century Dictionary]
vacuum (v.): "to clean with a vacuum cleaner," 1919, from vacuum (n.). Related: Vacuumed; vacuuming.
vade: Latin, imperative singular of vadere "to go" (see vamoose).
vade-mecum (n.): "a pocket manual, handbook," 1620s, Latin, literally "go with me;" from imperative of vadere "to go" (see vamoose) + me "me" + cum "with."
vae victis: Latin, literally "woe to the vanquished," from Livy, "History" V.xlviii.9.
vagabond (adj.): early 15c. (earlier vacabond, c. 1400), from Old French vagabond, vacabond "wandering, unsteady" (14c.), from Late Latin vagabundus "wandering, strolling about," from Latin vagari "wander" (from vagus "wandering, undecided;" see vague) + gerundive suffix -bundus.
vagabond (n.): c. 1400, earlier wagabund (in a criminal indictment from 1311); see vagabond (adj.). Despite the earliest use, in Middle English often merely "one who is without a settled home, a vagrant" but not necessarily in a bad sense. Notion of "idle, disreputable person" predominated from 17c.
vagal (adj.): "pertaining to the vagus," 1846, from vagus + -al (1).
vagary (n.): 1570s, "a wandering, a roaming journey," from Italian vagare or directly from Latin vagari "to wander, stroll about, roam, be unsettled, spread abroad," from vagus "roving, wandering" (see vague). The infinitive appears to have been adopted in English as a noun and conformed to nouns in -ary, "but this can hardly be explained except as an orig. university use" [Century Dictionary]. Current meaning of "eccentric notion or conduct" (1620s) is from notion of mental wandering. Related: Vagaries.
vagina (n.): "sexual passage of the female from the vulva to the uterus," 1680s, medical Latin, from specialized use of Latin vagina "sheath, scabbard, covering; sheath of an ear of grain, hull, husk" (plural vaginae), from PIE *wag-ina- (source also of Lithuanian vožiu "ro cover with a hollow thing"), from root *wag- "to break, split, bite." Probably the ancient notion is of a sheath made from a split piece of wood (see sheath). A modern medical word; the Latin word was not used in an anatomical sense in classical times. Anthropological vagina dentata is attested from 1902.
vaginal (adj.): 1726, "pertaining to a sheath," from vagina + -al (1). From 1800 as "pertaining to the vagina of a female." Related: Vaginally.
vaginismus (n.): "spasmodic narrowing of the orifice of the vagina," 1861, medical Latin, from vagina + -ismus (see -ism).
vaginitis (n.): "inflammation of the vagina," 1833, medical Latin; see vagina + -itis "inflammation."
vagitus (n.): crying of a newborn child, 1650s, from Latin vagitus "a crying, squalling," from vagire (see sough (v.)).
vagrancy (n.): "life of idle begging," 1706, from vagrant + -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.
vagrant (n.): 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 intrusive -r-. Middle English also had vagaunt "wandering, without fixed abode" (late 14c.), from Old French vagant.
vagrant (adj.): 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.
vague (adj.): "uncertain as to specifics," 1540s, from Middle French vague "empty, vacant; wild, uncultivated; wandering" (13c.), from Latin vagus "strolling, wandering, rambling," figuratively "vacillating, uncertain," of unknown origin. Related: Vagueness.
vaguely (adv.): 1748, from vague + -ly (2).
vagus (n.): plural vagi, 1840, "pneumogastric nerve," the long, widely distributed nerve from the brain to the upper body, from Latin vagus "wandering, straying" (see vague).
vail (n.): "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.)).
vain (adj.): 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 *wa-no-, from root *eue- "to leave, abandon, give out" (source also of Old English wanian "to lessen," wan "deficient;" Old Norse vanta "to lack;" Latin vacare "to be empty," vastus "empty, waste;" Avestan va- "lack," Persian vang "empty, poor;" Sanskrit una- "deficient," Armenian unain "empty").

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.
vainglorious (adj.): early 15c., from vainglory + -ous, or from Old French vain glorios "boastful, swaggering." Related: Vaingloriously; vaingloriousness. Groce ("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."
vainglory (n.): c. 1200, "worthless glory, undue pomp or show," waynglori, from Old French vaine glorie, from Medieval Latin vana gloria (see vain + glory (n.)).
vair (n.): "squirrel fur," or some other kind of fur in use in the Middle Ages, c. 1300, from Old French vair "two-toned squirrel fur; fur garments" (12c.), from Latin varium, masculine accusative singular of varius "parti-colored" (see vary). Gray or black above and white below.
valance (n.): piece of hanging, decorative drapery, mid-15c., of uncertain origin, probably from Anglo-French *valaunce, valence, from valer "go down, let down," variant of Old French avaler "descend, go down;" or possibly from the plural of Old French avalant, from present participle of avaler "go down." The notion is of something "hanging down." Not now considered to be from the name of Valence in southwestern France, which is from the Roman personal name Valentius. Related: Valenced.
vale (n.): river-land between two ranges of hills, early 14c., from Old French val "valley, vale" (12c.), from Latin vallem (nominative vallis, valles) "valley" (see valley). Now "little used except in poetry" [Century Dictionary]. Vale of years "old age" is from "Othello." Vale of tears "this world as a place of trouble" is attested from 1550s.
valediction (n.): "a farewell, a bidding farewell," 1610s, from past participle stem of Latin valedicere "bid farewell, take leave," from vale "farewell!," second person singular imperative of valere "be well, be strong" (see valiant) + dicere "to say" (see diction).
valedictorian (n.): "student who pronounces the oration at commencement exercises of his or her class," 1832, American English, from valedictory + -ian. As an adjective from 1834.
valedictory (adj.): 1650s, "pertaining or relating to leave-taking," from Latin valedictum (past participle of valedicere; see valediction) + -ory. As a noun meaning "valedictory address" from 1779.
valence (n.): early 15c., "extract, preparation," from Latin valentia "strength, capacity," from valentem (nominative valens) "strong, stout, vigorous, powerful," present participle of valere "be strong" (see valiant). Meaning "relative combining capacity of an element" is recorded from 1884, from German Valenz (1868), from the Latin word. Related: Valency.
Valencia: place in Spain, Roman Valentia Edetanorum "fort of the Edetani," a local people name; the first element from Latin valentia "strength" (see valence (n.)).
Valentine (n.): mid-15c., "sweetheart chosen on St. Valentine's Day," from Late Latin Valentinus, the name of two early Italian saints (from Latin valentia "strength, capacity;" see valence). Choosing a sweetheart on this day originated 14c. as a custom in English and French court circles. Meaning "letter or card sent to a sweetheart" first recorded 1824. The romantic association of the day is said to be from it being around the time when birds choose their mates.
For this was on seynt Volantynys day
Whan euery bryd cometh there to chese his make.
[Chaucer, "Parlement of Foules," c. 1381]
Probably the date was the informal first day of spring in whatever French region invented the custom (many surviving medieval calendars reckon the start of spring on the 7th or 22nd of February). No evidence connects it with the Roman Lupercalia (an 18c. theory) or to any romantic or avian quality in either of the saints. The custom of sending special cards or letters on this date flourished in England c. 1840-1870, declined around the turn of the 20th century, and revived 1920s.
To speak of the particular Customs of the English Britons, I shall begin with Valentine's Day, Feb. 14. when young Men and Maidens get their several Names writ down upon Scrolls of Paper rolled up, and lay 'em asunder, the Men drawing the Maidens Names, and these the Mens; upon which, the Men salute their chosen Valentines and present them with Gloves, &c. This Custom (which sometimes introduces a Match) is grounded upon the Instinct of Animals, which about this Time of the Year, feeling a new Heat by the approach of the Sun, begin to couple. ["The Present State of Great Britain and Ireland" London, 1723]