Etymology
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artillery (n.)

late 14c., "warlike munitions," especially ballistic engines, from Anglo-French artillerie, Old French artillerie (14c.), from artillier "to provide with engines of war" (13c.), which probably is from Medieval Latin articulum "art, skill," a diminutive of Latin ars (genitive artis) "art." But some would connect it to Latin articulum "joint," others to Latin apere "to attach, join," and still others to Old French atillier "to equip," altered by influence of arte.

Originally any engine for discharging missiles (catapults, slings, bows, etc.); the modern restriction to "ordnance, large guns" is from 16c. Technically, "all firearms discharged from carriages," as opposed to small arms, discharged by hand. As a branch of the army, from 1786.

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unit (n.)

1560s, "single number regarded as an undivided whole," alteration of unity on the basis of digit. Popularized in John Dee's English translation of Euclid, to express Greek monas (Dee says unity formerly was used in this sense). Meaning "single thing regarded as a member of a group" is attested from 1640s. Extended sense of "a quantity adopted as a standard of measure" is from 1738. Sense of "group of wards in a hospital" is attested from 1893.

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battery (n.)

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).

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cannonade (n.)

"a continued discharge of artillery," 1650s, from cannon + -ade. As a verb, "attack with artillery," from 1660s. Compare French canonnade (16c.), Italian cannonata. Related: Cannonaded; cannonading.

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photon (n.)

"unit of electromagnetic radiation," 1926, from photo- "light" + -on "unit." Related: Photonic.

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unitary (adj.)

1847, "characterized by unity or uniformity;" 1865, "of or relating to a unit;" see unit + -ary.

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artillerist (n.)

"person skilled in gunnery," 1778; see artillery + -ist. Artilleryman is from 1630s. Middle English had artiller "maker of arms" (mid-15c.), from Old French artiller.

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monad (n.)

1610s, "unity, arithmetical unit," 1610s, from Late Latin monas (genitive monadis), from Greek monas "unit," from monos "alone" (from PIE root *men- (4) "small, isolated"). In Leibnitz's philosophy, "an ultimate unit of being, a unit of the universal substance" (1748); he apparently adopted the word from Giordano Bruno's 16c. metaphysics, where it referred to a hypothetical primary indivisible substance at once material and spiritual. Related: Monadic; monadism.

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B.T.U. 

1889 as an abbreviation of British Thermal Unit (1862), a commercial unit of electrical energy (the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit); the French Thermal Unit is the amount of heat required to raise 1 kilogram of water 1 degree centigrade. Also from 1889 as an abbreviation of Board of Trade Unit, in electicity "1,000 watt hours."

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Dahlgren (n.)

type of cast-iron smooth-bore naval artillery cannon, by 1854, named for its inventor, U.S. naval ordnance officer John A. Dahlgren (1809-1870), who was of Swedish ancestry.

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