Etymology
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Selene 

moon goddess, equivalent of Latin Luna, from Greek selēnē "the moon; name of the moon goddess," related to selas "light, brightness, bright flame, flash of an eye," from PIE root *swel- (2) "to shine, beam" (source also of Sanskrit svargah "heaven," Lithuanian svilti "to singe," Old English swelan "to be burnt up," Middle Low German swelan "to smolder"); related to swelter, sultry. Related: Selenian "of or pertaining to the moon as a world," 1660s.

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selenographer (n.)
"student of the moon," 1660s, from selenography (1640s), from combining form of Selene + -graphy.
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selenium (n.)
element name, Modern Latin, from Greek selene "moon" (see Selene). Named by Berzelius (1818), on analogy of tellurium, with which it had been at first confused, and which was named for the earth. Despite the -ium ending it is not a metal and a more appropriate name selenion has been proposed.
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swelter (v.)
c. 1400, "faint with heat," frequentative of swelten "be faint (especially with heat)," late 14c., from Old English sweltan "to die, perish," from Proto-Germanic *swiltan- (source also of Old Saxon sweltan "to die," Old Norse svelta "to put to death, starve," Gothic sviltan "to die"), perhaps originally "to burn slowly," hence "to be overcome with heat or fever," from PIE root *swel- (2) "to shine, beam" (see Selene). From the same ancient root comes Old English swelan "to burn." For specialization of words meaning "to die," compare starve. Related: Sweltered; sweltering.
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Endymion 
beautiful youth, son of Jupiter and Calyce, beloved by Moon-goddess Selene, from Greek, perhaps literally "diver, plunger," from endyein "to enter into, sink into, plunge, dive," which was used in reference to the sun or stars setting into the sea. On this theory, he originally was a solar deity, a personification of the setting sun.
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luna (n.)
late 14c. "the moon," especially as personified in a Roman goddess answering to Greek Selene; also an alchemical name for "silver;" from Latin luna "moon, goddess of the moon," from PIE *leuksna- (source also of Old Church Slavonic luna "moon," Old Prussian lauxnos "stars," Middle Irish luan "light, moon"), suffixed form of root *leuk- "light, brightness." The luna moth (1841, American English) so called for the crescent-shaped eye-spots on its wings.
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month (n.)

"one-twelfth part of a year; one of the twelve parts into which the calendar year is arbitrarily divided," Old English monað, from Proto-Germanic *menoth- (source also of Old Saxon manoth, Old Frisian monath, Middle Dutch manet, Dutch maand, Old High German manod, German Monat, Old Norse manaðr, Gothic menoþs "month"), which is related to *menon- "moon" (see moon (n.)). Originally the month was the interval between one new moon and the next (a sense attested from late Old English).

Its cognates mean only "month" in the Romance languages, but in Germanic they generally continue to do double duty. The development of the calendrical meaning for words from this root in Greek (mēn) and Latin (mensis) was accompanied by the creation of new words for "moon" (selēnē, luna). The phrase a month of Sundays "a very long time" is from 1832 (roughly 7 and a half months but never used literally).

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lunatic (adj.)

late 13c., "affected with periodic insanity dependent on the changes of the moon," from Old French lunatique "insane," or directly from Late Latin lunaticus "moon-struck," from Latin luna "moon" (see luna).

Compare Old English monseoc "lunatic," literally "moon-sick;" Middle High German lune "humor, temper, mood, whim, fancy" (German Laune), from Latin luna. Compare also New Testament Greek selēniazomai "be epileptic," from selēnē "moon." Lunatic fringe (1913) apparently was coined by U.S. politician Theodore Roosevelt.

Then, among the wise and high-minded people who in self-respecting and genuine fashion strive earnestly for peace, there are foolish fanatics always to be found in such a movement and always discrediting it — the men who form the lunatic fringe in all reform movements. [Theodore Roosevelt, autobiography, 1913].

Earlier it was a term for a type of hairstyle worn over the forehead (1877). Lunatic soup (1918) was slang for "alcoholic drink" or in reference to drinking several different alcoholic drinks together.

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moon (n.)

"heavenly body which revolves about the earth monthly," Middle English mone, from Old English mona, from Proto-Germanic *menon- (source also of Old Saxon and Old High German mano, Old Frisian mona, Old Norse mani, Danish maane, Dutch maan, German Mond, Gothic mena "moon"), from PIE *me(n)ses- "moon, month" (source also of Sanskrit masah "moon, month;" Avestan ma, Persian mah, Armenian mis "month;" Greek mene "moon," men "month;" Latin mensis "month;" Old Church Slavonic meseci, Lithuanian mėnesis "moon, month;" Old Irish mi, Welsh mis, Breton miz "month"), from root *me- (2) "to measure" in reference to the moon's phases as an ancient and universal measure of time.

A masculine noun in Old English. In Greek, Italic, Celtic, and Armenian the cognate words now mean only "month." Greek selēnē (Lesbian selanna) is from selas "light, brightness (of heavenly bodies)." Old Norse also had tungl "moon," ("replacing mani in prose" - Buck), evidently an older Germanic word for "heavenly body," cognate with Gothic tuggl, Old English tungol "heavenly body, constellation," of unknown origin or connection. Hence Old Norse tunglfylling "lunation," tunglœrr "lunatic" (adj.).

Extended 1665 to satellites of other planets. Typical of a place impossible to reach or a thing impossible to obtain, by 1590s. Meaning "a month, the period of the revolution of the moon about the earth" is from late 14c.

To shoot the moon "leave without paying rent" is British slang from c. 1823 (see shoot (v.)); the card-playing sense perhaps was influenced by gambler's shoot the works (1922) "go for broke" in shooting dice. The moon race and the U.S. space program of the 1960s inspired a number of coinages, including, from those skeptical of the benefits to be gained, moondoggle (based on boondoggle). The man in the moon "fancied semblance of a man seen in the disk of the full moon" is mentioned since early 14c.; he carries a bundle of thorn-twigs and is accompanied by a dog. Some Japanese, however, see a rice-cake-making rabbit in the moon. The old moon in the new moon's arms (1727) is the appearance of the moon in the first quarter, in which the whole orb is faintly visible by earthshine.

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trivia (n.)

"trivialities, bits of information of little consequence," by 1932, from the title of a popular book by U.S.-born British aphorist Logan Pearsall Smith (1865-1946) first published in 1902 but popularized in 1918 (with "More Trivia" following in 1921 and a collected edition including both in 1933), containing short essays often tied to observation of small things and commonplace moments. Trivia is Latin, plural of trivium "place where three roads meet;" in transferred use, "an open place, a public place." The adjectival form of this, trivialis, meant "public," hence "common, commonplace" (see trivial).

The Romans also had trivius dea, the "goddess of three ways," another name for Hecate, perhaps originally in her triple aspect (Selene/Diana/Proserpine), but also as the especial divinity of crossroads (Virgil has "Nocturnisque hecate triviis ululata per urbes"). John Gay took this arbitrarily as the name of a goddess of streets and roads for his mock Georgic "Trivia: Or, the Art of Walking the Streets of London" (1716); Smith writes in his autobiography that he got the title from Gay.

I KNOW too much; I have stuffed too many of the facts of History and Science into my intellectuals. My eyes have grown dim over books; believing in geological periods, cave dwellers, Chinese Dynasties, and the fixed stars has prematurely aged me. ["Trivia," 1918 edition]

Then noted c. 1965 as an informal fad game among college students wherein one asked questions about useless bits of information from popular culture ("What was Donald Duck's address?") and others vied to answer first.

Nobody really wins in this game which concentrates on sports, comics and television. Everyone knows that Amos's wife on the "Amos 'n' Andy Show" is Ruby, but who knows that she is from Marietta, Georgia? Trivia players do. They also know the fourth man in the infield of Tinker-to-Evers-to-Chance, the Canadian who shot down Baron Von Richtofen, and can name ten Hardy Boy books. [Princeton Alumni Weekly, Nov. 9, 1965]

The board game Trivial Pursuit was released 1982 and was a craze in U.S. for several years thereafter.

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