Etymology
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vault (n.1)
"arched roof or ceiling," c. 1300, vaute, from Old French voute "arch, vaulting, vaulted roof or chamber," from Vulgar Latin *volta, contraction of *volvita, noun use of fem. of *volvitus, alteration of Latin volutus "bowed, arched," past participle of volvere "to turn, turn around, roll," from PIE root *wel- (3) "to turn, revolve." The -l- appeared in English c. 1400, an etymological insertion in imitation of earlier forms (compare fault (n.), assault (n.)).
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vault (v.1)

"jump or leap over," especially by aid of the hands or a pole, 1530s, transitive (implied in vaulting); 1560s, intransitive, from French volter "to gambol, leap," from Italian voltare "to turn," from Vulgar Latin *volvitare "to turn, leap," frequentative of Latin volvere "to turn, turn around, roll" (from PIE root *wel- (3) "to turn, revolve"). Related: Vaulted; vaulting.

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vault (n.2)
"a leap," especially using the hands or a pole, 1570s, from vault (v.1).
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vault (v.2)
"to form with a vault or arched roof," late 14c., from Old French vaulter, volter, from voute "arch, vaulted roof" (see vault (n.1)). Related: Vaulted; vaulting.
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pole-vault (n.)

"a jump over a horizontal bar by means of a pole," 1877, from pole (n.1) + vault (n.2). As a verb from 1892 (implied in pole-vaulting). Related: Pole-vaulted; pole-vaulter.

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archivolt (n.)
ornamental molding on the face of an arch, 1731, from Italian archivolto, from volta, volto "arch, vault" (see vault (n.1)).
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cavort (v.)

1793, cauvaut, "to prance, bustle nimbly or eagerly," American English, of uncertain origin, sometimes said to be an alteration of curvet "a leap by a horse," a word from French that is related to curve (v.). Or perhaps from ca-, ka-, colloquial intensive prefix + vault (v.) "to jump, leap." Modern form attested by 1829. Related: Cavorted; cavorting.

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assault (n.)
late 14c., earlier asaut (c. 1200), "physical attack (on a person), sudden violent onslaught (on a place)," from Old French asaut, assaut "an attack, an assault, attacking forces" (12c.), from Vulgar Latin *adsaltus "attack, assault," from ad "to" (see ad-) + Latin saltus "a leap," from salire "to leap, spring" (see salient (adj.)). The -l- was restored, as in fault (n.), vault (n.1). In law by 1580s; historically, assault includes menacing words or actions coupled with present means to effect them; battery is an actual blow.
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*wel- (3)
Proto-Indo-European root meaning "to turn, revolve," with derivatives referring to curved, enclosing objects.

It forms all or part of: archivolt; circumvolve; convoluted; convolution; devolve; elytra; evolution; evolve; Helicon; helicopter; helix; helminth; lorimer; ileus; involve; revolt; revolution; revolve; valve; vault (v.1) "jump or leap over;" vault (n.1) "arched roof or ceiling;" volte-face; voluble; volume; voluminous; volute; volvox; volvulus; vulva; wale; walk; wallet; wallow; waltz; well (v.) "to spring, rise, gush;" welter; whelk; willow.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit valate "turns round," ulvam "womb, vulva;" Lithuanian valtis "twine, net," vilnis "wave," apvalus "round;" Old Church Slavonic valiti "roll, welter," vlŭna "wave;" Greek eluein "to roll round, wind, enwrap," eilein "twist, turn, squeeze; revolve, rotate," helix "spiral object;" Latin volvere "to turn, twist;" Gothic walwjan "to roll;" Old English wealwian "roll," weoloc "whelk, spiral-shelled mollusk;" Old High German walzan "to roll, waltz;" Old Irish fulumain "rolling;" Welsh olwyn "wheel."
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undercroft (n.)
"crypt of a church; underground vault," late 14c., from under + croft.
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