Etymology
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climate change (n.)

1983, in the modern "human-caused global warming" sense. See climate (n.) + change (n.). Climatic change in a similar sense was in use from 1975.

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plus ca change 

phrase expressing the fundamental immutability of life, human situations, etc., 1903, French, plus ça change, plus c'est la même chose (1849), literally "the more it changes, the more it stays the same."

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mutatis mutandis 
"with the necessary changes," Latin, literally "things being changed that have to be changed," from the ablative plurals of, respectively, the past participle and gerundive of mutare "to change" (from PIE root *mei- (1) "to change, go, move").
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light bulb (n.)
also lightbulb, 1884, from light (n.) + bulb (n.). Changing one as figurative of something easy to do is from 1920s; jokes about how many of a certain type it takes to change one date from 1971.
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coup d'etat (n.)

1640s, from French coup d'étate, literally "stroke of the state" (see coup). Technically any sudden, decisive political act, especially an important and unexpected change in the form and methods of a government, but in 20c. popularly restricted to the overthrow of a government.

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vice versa 

"the order being changed," c. 1600, Latin, from vice, ablative of vicis "a change, alternation, alternate order" (from PIE root *weik- (2) "to bend, to wind") + versa, feminine ablative singular of versus, past participle of vertere "to turn, turn about" (from PIE root *wer- (2) "to turn, bend"). "The phrase has the complete force of a proposition, being as much as to say that upon a transposition of antecedents the consequents are also transposed" [Century Dictionary].

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lucus a non lucendo 

a phrase that stands for "absurd etymology," or generally "anything illogical, outrageous hypothesis," 1711, from the Latin phrase, taken as the outstanding example of such an error.

"A grove (lucus) [is so called] from not (a non) being light" (lucendo, ablative of lucere "to shine;" see light (n.)). That is, it is called a grove because light doesn't get into it. This explanation is found in a commentary on Virgil (Aeneid 1.22) by Servius, a 4th century grammarian, among other places. Other ancient grammarians (notably Quintilian) found it paradoxical and absurd, based on nothing more than the similarity in sound between the two words.

Modern scholarship, however, concludes that lucus and lucere probably do come both from the same PIE root (*leuk-) meaning "light, bright." De Vaan writes: "Lucus 'sacred grove, wood,' from PIE *louk-o- 'light place,' with cognates in Sanskrit loka- 'free space, world,' Lithuanian laukas 'field, land,' Latvian lauks 'field, clearing in the woods,' Old High German loh 'clearing' and English lea 'open field, meadow, piece of untilled grassy ground.' " Apparently the primeval notion in *louk-o- was a lighter place in a thick forest. Migration, change of climate, or felling of the woods might have shifted the meaning.

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