Etymology
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genius (n.)

late 14c., "tutelary or moral spirit" who guides and governs an individual through life, from Latin genius "guardian deity or spirit which watches over each person from birth; spirit, incarnation; wit, talent;" also "prophetic skill; the male spirit of a gens," originally "generative power" (or "inborn nature"), from PIE *gen(e)-yo-, from root *gene- "give birth, beget," with derivatives referring to procreation and familial and tribal groups.

The sense of "characteristic disposition" of a person is from 1580s. The meaning "person of natural intelligence or talent" and that of "exalted natural mental ability, skill in the synthesis of knowledge derived from perception" are attested by 1640s.

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genii (n.)
Latinate English plural of genius.
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genie (n.)
1650s, "tutelary spirit," from French génie, from Latin genius (see genius); used in French translation of "Arabian Nights" to render Arabic jinni, singular of jinn, which it accidentally resembled, and attested in English with this sense from 1748.
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eudaemonic (adj.)

also eudemonic, "producing happiness," 1856, from Greek eudaimonikos "conducive to happiness," from eudaimonia "happiness," from eu "good" (see eu-) + daimōn "guardian, genius" (see daimon). Related: Eudaimonia; eudemonia; eudaemonical.

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dustman (n.)

1707, "one employed in the removal of dust, rubbish, and garbage," from dust (n.) + man (n.). As the genius of sleep in popular sayings and folklore, by 1821.

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jinn (n.)
1680s, djen, from Arabic jinn. It is a collective plural, "demons, spirits, angels;" the proper singular is jinni, which appears in English occasionally as jinnee (1840) but more frequently as genie. Similarity to genius is accidental.
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Nimzo-Indian (adj.)

type of defensive opening in chess, 1935, in reference to Aron Nimzowitsch (1886-1935), Latvian-born Jewish chess genius who popularized a variation of the Indian defense (1884) attributed to Indian chess player Moheschunder Bannerjee.

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ethos (n.)

"the 'genius' of a people, characteristic spirit of a time and place," 1851 (Palgrave) from Greek ēthos "habitual character and disposition; moral character; habit, custom; an accustomed place," in plural, "manners," from suffixed form of PIE root *s(w)e- third person pronoun and reflexive (see idiom). An important concept in Aristotle (as in "Rhetoric" II xii-xiv).

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genial (adj.)
1560s, "pertaining to marriage," from Latin genialis "pleasant, festive," originally "pertaining to marriage rites," from genius "guardian spirit," with here perhaps a special sense of "tutelary deity of a married couple," from PIE *gen(e)-yo-, from root *gene- "give birth, beget," with derivatives referring to procreation and familial and tribal groups. Originally used in English in the Latin literal sense; meaning "cheerful, friendly" first recorded 1746. Related: Genially.
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battalion (n.)

1580s, from French bataillon (16c.), from Italian battaglione "battle squadron," from diminutive of Vulgar Latin *battalia "battle," from Latin bauttere "to beat" (see batter (v.)). Specific sense of "part of a regiment" is from 1708. The oft-repeated quote "God is on the side of the largest battalions" (with many variants) usually is attributed to 17c. French military genius and marshal Turenne:

Madame, lui répondit-il, ne vous y fiez pas: j'ay tôujours vû Dieu do coté des gros Batallions. [E.Boursault, 1702]
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