Etymology
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incest (n.)
"the crime of sexual intercourse between near kindred," c. 1200, from Old French inceste "incest; lechery, fornication," and directly from Latin incestum "unchastity, impious unchastity," also specifically "sexual intercourse between close relatives," noun use of neuter adjective incestus "unchaste, impure," from in- "not" (see in- (1)) + castus "pure" (see caste). Old English had sibleger "incest," literally "kin-lying."
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taboo (adj.)
also tabu, 1777 (in Cook's "A Voyage to the Pacific Ocean"), "consecrated, inviolable, forbidden, unclean or cursed," explained in some English sources as being from Tongan (Polynesian language of the island of Tonga) ta-bu "sacred," from ta "mark" + bu "especially." But this may be folk etymology, as linguists in the Pacific have reconstructed an irreducable Proto-Polynesian *tapu, from Proto-Oceanic *tabu "sacred, forbidden" (compare Hawaiian kapu "taboo, prohibition, sacred, holy, consecrated;" Tahitian tapu "restriction, sacred, devoted; an oath;" Maori tapu "be under ritual restriction, prohibited"). The noun and verb are English innovations first recorded in Cook's book.
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incestuous (adj.)
1530s, from Late Latin incestuosus "incestuous," from Latin incestus "unchaste" (see incest). Figurative use is from 1744. Related: Incestuously; incestuousness.
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black comedy (n.)

1961, "comedy that deals in themes and subjects usually regarded as serious or taboo," from black (adj.), in a figurative sense of "morbid," + comedy. Compare French pièce noire, also comédie noire "macabre or farcical rendering of a violent or tragic theme" (1958, perhaps the inspiration for the English term) and 19th-century gallows-humor. In a racial sense, from 1921.

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*kes- 
Proto-Indo-European root meaning "to cut."

It forms all or part of: caret; cashier (v.) "dismiss;" cassation; caste; castellan; castellated; Castile; castle; castigate; castrate; castration; chaste; chastity; chateau; chatelaine; Chester; forecastle; incest; quash (v.) "make void, annul."

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit sastra- "knife, dagger;" Greek keazein "to split;" Latin carere "to be cut off from," cassus "empty, void;" Old Church Slavonic kosa "scythe."
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Jap (n.)
colloquial abbreviation of Japanese, 1877, perhaps encouraged or inspired by the common abbreviation Jap.; it was not originally pejorative, but it became intensely so during World War II. It was protested by Japanese before the war, but did not begin to be taboo in the U.S. before 1960s. As an adjective from 1878. For some years after World War II in American English the word also functioned as a verb, "to execute a sneak attack upon," a reference to Pearl Harbor.
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minnesinger (n.)

one of a class of medieval German poets who imitated the troubadours, 1825, from German minnesinger, from minne "love," especially "sexual love" (from Old High German minna "loving memory," originally "memory," from Proto-Germanic *minthjo, from PIE *menti-, suffixed form of root *men- (1) "to think") + singer (see singer). German minne by c. 1500 no longer was considered decent, and it became a taboo word until revived 18c. in poetic language. Compare meisitersinger. Related: Minnelied "love-song."

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abuse (v.)
Origin and meaning of abuse
early 15c., "to misuse, misapply" (power, money, etc.), from Old French abuser "deceive, abuse, misuse" (14c.), from Vulgar Latin *abusare, from Latin abusus "an abusing; a using up," past participle of abuti "use up, consume," also "misuse, abuse, misapply, outrage," from ab "off, away from" (see ab-) + uti "use" (see use).

Also in reference to forbidden sexual situations from early 15c., but originally meaning incest, masturbation (self-abuse), homosexuality, prostitution, etc. From 1550s specifically as "to misuse sexually, ravish," but OED 2nd ed. marks this obsolete and the modern use "subject (someone) to unwanted sexual activity" is likely a fresh coinage from late 20c. Specifically of drugs, from 1968. Meaning "attack with harsh language, revile" is from c. 1600. Related: Abused; abusing.
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homosexual (adj.)

1892, in C.G. Chaddock's translation of Krafft-Ebing's "Psychopathia Sexualis," from German homosexual, homosexuale (by 1880, in Gustav Jäger), from Greek homos "same" (see homo- (1)) + Latin-based sexual.

'Homosexual' is a barbarously hybrid word, and I claim no responsibility for it. It is, however, convenient, and now widely used. 'Homogenic' has been suggested as a substitute. [H. Havelock Ellis, "Studies in Psychology," 1897]

Sexual inversion (1883, later simply inversion, by 1895) was an earlier clinical term for "homosexuality" in English, said by Ellis to have originated in Italian psychology writing. See also uranian. Unnatural love was used 18c.-19c. for homosexuality as well as pederasty and incest. In 17c.-18c., pathic was used as a noun and adjective in reference to a man that submits to sexual intercourse with another man. Related: Homosexually.

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adjective (n.)

"word used to qualify, limit, or define a noun or noun-like part of speech," late 14c., short for noun adjective, from Old French adjectif (14c.), from Latin adjectivum "that is added to (the noun)," neuter of adjectivus "added," past participle of adicere "throw to, fling at, throw or place (a thing) near," especially "add in addition, add by way of increase," from ad "to" (see ad-) + combining form of iacere "to throw" (from PIE root *ye- "to throw, impel"). In Britain from at least 1851 the word often was a euphemism for the taboo adjective bloody.

They ... slept until it was cool enough to go out with their 'Towny,' whose vocabulary contained less than six hundred words, and the Adjective. [Kipling, "Soldiers Three," 1888]
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