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.

"attack physically," early 15c., assauten, from Old French asauter, assauter, from Vulgar Latin *assaltare (see assault (n.)). Related: Assaulted; assaulting.

"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.)).

amphibious assault vehicle, 1944, contraction of amphibious tractor (n.).

also defenceless, "being without means of repelling assault or injury," 1520s, from defense + -less. Related: Defenselessly; defenselessness.

mid-15c., invasioun, "an assault, attack, act of entering a country or territory as an enemy," from Old French invasion "invasion, attack, assault" (12c.), from Late Latin invasionem (nominative invasio) "an attack, invasion," noun of action from past-participle stem of Latin invadere "to go, come, or get into; enter violently, penetrate into as an enemy, assail, assault, make an attack on," from in- "in" (from PIE root *en "in") + vadere "to go, to walk, go hastily," from PIE root *wadh- (2) "to go" (source also of Old English wadan "to go," Latin vadum "ford;" see wade (v.)).

In extended sense, of diseases, "a harmful incursion of any kind;" with reference to rights, etc., "infringement by intrusion, encroachment by entering into or taking away what belongs to another."

also rapeable, "Of a person: regarded as a suitable object for sexual pursuit or assault" [OED], 1972, from rape (v.) + -able.

1610s, from past participle stem of Medieval Latin assassinare (see assassin). "Assassinate means to kill wrongfully by surprise, suddenly, or by secret assault" [Century Dictionary]. Of reputations, characters, etc., from 1620s. Related: Assassinated; assassinating.

1530s, "a putting forth of effort in some difficult or uncertain endeavor," from attempt (v.). The meaning "effort to accomplish something by violence" is from 1580s, especially as an assault on someone's life.