Etymology
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blackamoor (n.)
"dark-skinned person, black-skinned African," 1540s, from black (adj.) + Moor, with connecting element.
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blackboard (n.)
"board painted black and written on in chalk," especially as used in schoolrooms, 1823, from black + board (n.1). Blackboard jungle "inner-city school rife with juvenile delinquency" is from Evan Hunter's novel title (1954).
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blacken (v.)
c. 1200, "become black or dark;" early 14c., "make black, darken, dye (hair);" see black (adj.) + -en (1). Figurative sense of "to besmirch" (with dishonor, etc.) is from early 15c. Related: Blackened; blackening.
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black code (n.)
local or state legal restrictions on black persons, free or slave, 1774, American English, though the first reference is to French colonies in the West Indies.
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black swan (n.)

proverbial for "something extremely rare or non-existent" (late 14c.) is from Juvenal ["Sat." vi. 164], but the real thing turned up in Australia (Chenopsis atratus).

"Do you say no worthy wife is to be found among all these crowds?" Well, let her be handsome, charming, rich and fertile; let her have ancient ancestors ranged about her halls; let her be more chaste than all the dishevelled Sabine maidens who stopped the war—a prodigy as rare upon the earth as a black swan! yet who could endure a wife that possessed all perfections? I would rather have a Venusian wench for my wife than you, O Cornelia, mother of the Gracchi, if, with all your virtues, you bring me a haughty brow, and reckon up Triumphs as part of your marriage portion. [Juvenal]

Blue dahlia also was used 19c. for "something rare and unheard of."

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blackball (v.)
also black-ball, "to exclude from a club by adverse votes," 1770, from black (adj.) + ball (n.1). The image is of the black balls of wood or ivory that were dropped into an urn as adverse votes during secret ballots. Related: Blackballed; blackballing.
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blackjack (n.)
used in various senses since 16c., earliest is possibly "tar-coated leather jug for beer" (1590s), from black (adj.) + jack in any of its many slang meanings. From 1867 as "pirate flag." The hand-weapon so called from 1889; the card game by 1900.
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black friar (n.)
"friar of the Dominican order," c. 1500, so called from the color of their dress.
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black hole (n.)
in astrophysics, 1968, probably with awareness of the notorious Black Hole of Calcutta, incident of June 19, 1756, in which 146 British POWs taken by the Nawab of Bengal after the capture of Ft. William, Calcutta, were held overnight in a punishment cell of the barracks (meant to hold 4 people) and all but 23 perished.
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Black Shirt (n.)
also blackshirt, 1922, member of Fasci di Combattimento, Italian paramilitary unit founded 1919 by Mussolini; so called for their uniforms.
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