Etymology
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fuel (n.)
c. 1200, feuel, feul "fuel, material for burning," also figurative, from Old French foaille "fuel for heating," from Medieval Latin legal term focalia "right to demand material for making fire, right of cutting fuel," from classical Latin focalia "brushwood for fuel," from neuter plural of Latin focalis "pertaining to a hearth," from focus "hearth, fireplace" (see focus (n.)). Figurative use from 1570s. Of food, as fuel for the body, 1876. As "combustible liquid for an internal combustion engine" from 1886. A French derivative is fouailler "woodyard." Fuel-oil is from 1882.
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curfew (n.)

early 14c., curfeu, "evening signal, ringing of a bell at a fixed hour" as a signal to extinguish fires and lights, from Anglo-French coeverfu (late 13c.), from Old French cuevrefeu, literally "cover fire" (Modern French couvre-feu), from cuevre, imperative of covrir "to cover" (see cover (v.)) + feu "fire" (see focus (n.)). Related: Curfew-bell (early 14c.).

The medieval practice of ringing a bell (usually at 8 or 9 p.m.) as an order to bank the hearths and prepare for sleep was to prevent conflagrations from untended fires. The modern extended sense of "periodic restriction of movement" had evolved by 1800s.

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-i (2)
plural suffix sometimes preserved in English for words from Latin, it is the Latin plural of nouns of the second declension (such as focus/foci, radius/radii).
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epicenter (n.)
1885 in seismology, "point on the earth's surface directly above the center or focus of an earthquake," from Modern Latin epicentrum (1879 in geological use); see epi- + center (n.). Related: Epicentral (1866).
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lioness (n.)
"female lion," c. 1300, leoness, from lion + -ess. From late 14c., of persons, "fierce or cruel woman." From 1590s as "woman who is boldly public;" from 1808 as "woman who is a focus of public interest."
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major (v.)

of a college or university student, "focus (one's) studies," 1910, American English, from major (n.) in sense of "subject of specialization" (by 1890). Related: Majored; majoring. Earlier as a verb, in Scottish, "to prance about, or walk backwards and forwards with a military air and step" [Jamieson, 1825] a sense derived from the military major.

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concentrate (v.)
Origin and meaning of concentrate

1630s, "to bring or come to a common center," from concenter (1590s), from Italian concentrare, from assimilated form of Latin com "with, together" (see con-) + centrum "center" (see center (n.)).

Meaning "condense" is from 1680s; that of "intensify the action of" is from 1758. Sense of "mentally focus" is from 1860s, on the notion of "concentrate the mind or mental powers." Related: Concentrated; concentrating.

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myopia (n.)

"short-sightedness," 1727, medical Latin, from Late Greek myōpia "near-sightedness," from myōps "near-sighted," literally "closing the eyes, blinking," on the notion of "squinting, contracting the eyes" (as near-sighted people do), from myein "to shut" (see mute (adj.)) + ōps (genitive ōpos) "eye" (from PIE root *okw- "to see"). By coincidence the name describes the problem: the parallel rays of light are brought to a focus before they reach the retina.

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cynosure (n.)

"something that strongly attracts attention," 1590s, from French cynosure (16c.), from Latin Cynosura, literally "dog's tail," an old name of the constellation (now Ursa Minor) containing what is now (but was not in ancient times) the North Star, the focus of navigation, at the tip of its tail; from Greek kynosoura, literally "dog's tail," from kyōn (genitive kynos; from PIE root *kwon- "dog") + oura "tail" (see arse). Apparently in ancient times the whole constellation was used as a rough indicator of the celestial north pole. Related: Cynosural.

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terminus (n.)

1550s, "goal, end, final point," from Latin terminus (plural termini) "an end, a limit, boundary line," from PIE *ter-men- "peg, post," from root *ter-, base of words meaning "peg, post; boundary, marker, goal" (source also of Sanskrit tarati "passes over, crosses over," tarantah "sea;" Hittite tarma- "peg, nail," tarmaizzi "he limits;" Greek terma "boundary, end-point, limit," termon "border;" Gothic þairh, Old English þurh "through;" Old English þyrel "hole;" Old Norse þrömr "edge, chip, splinter"). "The Hittite noun and the usage in Latin suggest that the PIE word denoted a concrete object which came to refer to a boundary-stone." [de Vaan]

In ancient Rome, Terminus was the name of the deity who presided over boundaries and landmarks, focus of the important Roman festival of Terminalia (held Feb. 23, the end of the old Roman year). The meaning "either end of a transportation line" is first recorded 1836.

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