1530s, "action of battering," in law, "the unlawful beating of another," from French batterie, from Old French baterie "beating, thrashing, assault" (12c.), from batre "to beat," from Latin battuere (see batter (v.)).

The meaning shifted in French from "bombardment" ("heavy blows" upon city walls or fortresses) to "unit of artillery" (a sense recorded in English from 1550s). The extension to "electrical cell" (1748, in Ben Franklin) is perhaps from the artillery sense via notion of "discharges" of electricity. In Middle English, bateri meant only "forged metal ware." In obsolete baseball jargon battery was the word for "pitcher and catcher" considered as a unit (1867, originally only the pitcher).

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.

of electrical devices or appliances, "working without a cord, battery-powered," 1905, from cord + -less.

1839, "apparatus for reversing the currents from a battery without rearranging the conductors," agent noun from Latin commutare (see commute (v.)). From 1880 as "contrivance for varying the strength of an electric current."

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.

also hydroelectric, 1827, "produced by a galvanic cell battery," which uses liquid, from hydro- "water" + electric. Meaning "generating electricity by force of moving water" is from 1884. Related: Hydroelectricity.

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."