Etymology
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redline (v.)

also red-line, "mark in red ink," 1820, from red (adj.1) + line (v.). Specific sense of "deny loans to certain neighborhoods based on ethnicity" is from 1973, on notion of lines drawn on maps. Used earlier in reference to insurance company practices (by 1956) and in World War II military slang in reference to a red line drawn through a soldier's name for some infraction, thus denying his pay. Related: Redlined; redlining.

Reports have been increasing here in the last few days to the effect that the American Automobile Association is "red lining" Warren County as a speed trap. [Park City Daily News, Bowling Green, Ky., March 9, 1956]
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libertine (n.)
late 14c., "a freedman, an emancipated slave," from Latin libertinus "condition of a freedman; member of a class of freedmen," from libertus "one's freedmen, emancipated person," from liber "free" (see liberal (adj.)).

Sense of "freethinker" is first recorded 1560s, from French libertin (1540s) originally the name given to certain pantheistic Protestant sects in France and the Low Countries. This sense partakes more of liberty and liberal than of the classical meaning (in Old French, libertin meant "Saracen slave converted to Christianity"). Meaning "dissolute or licentious person, man given to indulgence of lust" is first recorded 1590s; the darkening of meaning being perhaps due to misunderstanding of Latin libertinus in Acts vi:9. For "condition of being a libertine" 17c English tried libertinage; libertinism (from French libertinisme).
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poliomyelitis (n.)

1874, also polio-myelitis, coined by German physician Adolph Kussmaul (1822-1902) from Greek polios "grey" (from PIE root *pel- (1) "pale") + myelos "marrow" (a word of unknown origin) + -itis "inflammation." So called because the gray matter in the spinal cord is inflamed, which causes paralysis. The earlier name was infantile paralysis (1843).

In many respects, also, this affection resembles the acute spinal paralysis of infancy, which, from the researches of Charcot, Joffroy, and others, have been shown pathologically to be an acute myelitis of the anterior cornua. Hence, for these forms of paralysis, Professor Kussmaul suggests the name of 'poliomyelitis anterior.' [London Medical Record, Dec. 9, 1874]

Polioencephalitis (also poliencephalitis) "inflammation of the gray matter of the brain" is by 1885.

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tween (prep.)
also 'tween, c. 1300 as an abbreviation of between. As a noun meaning "child nearing puberty" (approximately ages 9 to 12), attested by 1988, in this case by influence of teen. Tolkien uses it in "Lord of the Rings" for "the irresponsible twenties between [Hobbit] childhood and coming of age at thirty-three." Earlier in this sense was subteen (1952). Related: Tweens. Tweenie or tweeny was a term (late 19c.-early 20c.) for "between-maid, a servant who assists two others" and was used in reference to other persons or objects in intermediary situations. And 'tween-age (adj.) was used in descriptions of clothing from 1937. Tween-ager is attested from 1946.
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prime (n.)

"earliest canonical hour of the day" (6 a.m.), from Old English prim and Old French prime and directly from Medieval Latin prima "the first service," from Latin prima hora "the first hour" (of the Roman day), from Latin primus "first, the first, first part" (see prime (adj.)).  (In classical Latin, the noun uses of the adjective meant "first part, beginning; leading place.")

By extension, "the first division of the day" 6 a.m. to 9 a.m. (early 13c.). The sense of "beginning of a period or course of events" is from late 14c. From the notion of "the period or condition of greatest vigor in life" (by 1530s) comes the specific sense "springtime of human life" (often meaning ages roughly 21 to 28) is from 1590s. Also from 1590s as "that which is best in quality, highest or most perfect state of anything." As "a prime number," by 1530s.

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Nimrod 

"great hunter," 1712, a reference to the biblical son of Cush, referred to (Genesis x.8-9) as "a mighty hunter before the Lord." In Middle English he was Nembrot (mid-13c.), founder of cities and builder of the tower of Babel (though Genesis does not name him as such). In 16c.-17c. his name was synonymous with "a tyrant." The word came to mean "geek, klutz" by 1983 in teenager slang, for unknown reasons. (Amateur theories include its occasional use in "Bugs Bunny" cartoon episodes featuring rabbit-hunting Elmer Fudd as a foil; its alleged ironic use, among hunters, for a clumsy member of their fraternity; or a stereotype of deer hunters by the non-hunting population in the U.S.)

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summer (n.1)

"hot season of the year," Old English sumor "summer," from Proto-Germanic *sumra- (source also of Old Saxon, Old Norse, Old High German sumar, Old Frisian sumur, Middle Dutch somer, Dutch zomer, German Sommer), from PIE root *sm- "summer" (source also of Sanskrit sama "season, half-year," Avestan hama "in summer," Armenian amarn "summer," Old Irish sam, Old Welsh ham, Welsh haf "summer").

As an adjective from c. 1300. Summer camp as an institution for youth is attested from 1886; summer resort is from 1823; summer school first recorded 1810; theatrical summer stock is attested from 1941 (see stock (n.2)). Old Norse sumarsdag, first day of summer, was the Thursday that fell between April 9 and 15.

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orthopraxy (n.)

"correct practice, action, or procedure," 1840, from ortho- + Greek praxis "a doing, action, performance" (see praxis).

Errata — Page 263, line 9 from bottom, for 'orthodoxy' read orthopraxy. This is a new coin from the mint of Dr. [Andrew] Wylie [of Bloomington College, Indiana], at least I have not before noticed it. Its etymology places it in a just contrast with orthodoxy: for if that consecrated word indicates thinking right, orthopraxy will legitimately import doing right, and hence, as Mr. Wylie says, orthopraxy in the last dread day will pass the divine ordeal incomparably better than orthodoxy. O! that a zeal for orthopraxy would transcend the zeal for orthodoxy! ["The Millennial Harbinger," vol. iv, no. 8, Bethany, Virginia, August 1840]
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song (n.)

Old English sang "voice, song, art of singing; metrical composition adapted for singing, psalm, poem," from Proto-Germanic *songwho- (source also of Old Norse söngr, Norwegian song, Swedish sång, Old Saxon, Danish, Old Frisian, Old High German, German sang, Middle Dutch sanc, Dutch zang, Gothic saggws), from PIE *songwh-o- "singing, song," from *sengwh- "to sing, make an incantation" (see sing (v.)).

Phrase for a song "for a trifle, for little or nothing" is from "All's Well" III.ii.9 (the identical image, por du son, is in Old French. With a song in (one's) heart "feeling joy" is first attested 1930 in Lorenz Hart's lyric. Song and dance as a form of vaudeville act is attested from 1872; figurative sense of "rigmarole" is from 1895.

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ninepence (n.)

"the sum of nine pennies," 1540s, from nine + pence. No coin of this value was ever issued in England, but the silver shilling issued by Queen Elizabeth for Ireland in 1561 were current in England for nine pence, and in New England it was the name of a Spanish silver coin worth about 9 pence of New England currency.

The ninepence was a coin formerly much favoured by faithful lovers in humble life, as a token of their mutual affection. It was for this purpose broken into two pieces, and each party preserved with care one portion, until on their meeting again, they hastened to renew their vows. [John Gough Nichols, "Anecdotes of the English Coinage," in The Numismatic Chronicle, 1839]
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