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).

also flash-light, 1886, "on-and-off signal light in a light-house, etc.," from flash (v.) + light (n.). As the word for a photographer's light-emitting preparation, 1892 (flash-lamp in this sense is by 1890). From 1905 as as a handheld, pocket-sized electric illumination device, the American English word for what the British might call an electric torch.

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."

mid-13c., from Old French torche "torch," also "handful of straw" (for wiping or cleaning, hence French torcher "to wipe, wipe down"), originally "twisted thing," then "torch formed of twisted tow dipped in wax," probably from Vulgar Latin *torca, alteration of Late Latin torqua, from Latin torquere "to twist" (from PIE root *terkw- "to twist").

In Britain, also applied to the battery-driven version (in U.S., a flashlight). To pass the torch is an ancient metaphor from the Greek torch-races (lampadedromia) where the goal was to reach the finish line with the torch still burning. Torch-bearer "leader of a cause" is from 1530s. Torch song is 1927 ("My Melancholy Baby," performed by Tommy Lyman, is said to have been the first so called), from carry a torch "suffer an unrequited love" (also 1927), Broadway slang, but the sense is obscure.

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.

initialism (acronym) from shit out of luck (though sometimes euphemised), 1917, World War I military slang. "Applicable to everything from death to being late for mess" [Russell Lord, "Captain Boyd's Battery, A.E.F.," c. 1920]

late 15c., "one who loads," agent noun from charge (v.). The meaning "war-horse, horse ridden in charging" is from 1762. The meaning "appliance for charging" in any sense is from 1711, originally in reference to firearms; from 1901 as "device to give charge to an electric battery."

also diehard, 1844, in reference to the 57th Regiment of Foot in the British Army, from the verbal phrase die hard "suffer, struggle, or resist in dying," 1784; see die (v.) + hard (adv.). As an adjective, attested from 1871. The  brand of automobile battery, spelled DieHard, was introduced by Sears in 1967.

"a putting or fixing in place; a place or site," 1742, formerly also implacement; from French emplacement "place, situation," from verb emplacer, from assimilated form of en- "in" (see en- (1)) + placer "to place" from place "place, spot" (see place (n.)). Military sense of "the space within a fortification allotted for the position and service of a gun or battery" is attested from 1811.