Etymology
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luminosity (n.)

1630s, "quality of being luminous," from French luminosité (cognate with Medieval Latin luminositas "splendor") or else a native formation from luminous + -ity. Meaning "intensity of light in a color" (of a flame, spectrum, etc.) is from 1876. In astronomy, "intrinsic brightness of a heavenly body" (as distinguished from apparent magnitude, which diminishes with distance), attested from 1906.

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lucency (n.)

"brightness, luster, luminosity," 1650s, from lucent + abstract noun suffix -cy. Lucence is from late 15c.

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phosphorescent (adj.)

shining with a faint light or luminosity like that of phosphorus, luminous without sensible heat," "1766, from Modern Latin phosphorus (see phosphorus) + -escent. Related: Phosphorescently.

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phosphorescence (n.)

"a property of certain bodies of becoming luminous without undergoing combustion," 1796, from French phosphorescence (1788) or from the English verb phosphoresce "emit luminosity without combustion" (1794; see phosphorous) + -ence.

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lumen (n.)

unit of luminosity, 1897, coined in French 1894 by French physicist André-Eugène Blondel (1863-1938) from Latin lumen "light" (n.), from suffixed form of PIE root *leuk- "light, brightness." Earlier it was used in anatomy for "an opening or passageway" (1873).

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hue (n.1)

"color," Old English hiw "color; form, appearance; species, kind; beauty," earlier heow, hiow, from Proto-Germanic *hiwam (source also of Old Norse hy "bird's down," Swedish hy "skin, complexion," Gothic hiwi "form, appearance"), from PIE *kiwo-, suffixed form of root *kei- (2), a color adjective of broad application (source also of Sanskrit chawi "hide, skin, complexion, color, beauty, splendor," Lithuanian šyvas "white").

A common word in Old English, squeezed into obscurity after c. 1600 by color (n.) but revived 1850s in chemistry and chromatography, often in a distinctive sense in reference to the quality of color other than luminosity and chroma.

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gray (adj.)

"of a color between white and black; having little or no color or luminosity," Old English græg "gray" (Mercian grei), from Proto-Germanic *grewa- "gray" (source also of Old Norse grar, Old Frisian gre, Middle Dutch gra, Dutch graw, Old High German grao, German grau), with no certain connections outside Germanic. French gris, Spanish gris, Italian grigio, Medieval Latin griseus are Germanic loan-words. The spelling distinction between British grey and U.S. gray developed 20c. Expression the gray mare is the better horse in reference to households ruled by wives is recorded from 1540s.

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red (n.)

 "the color red; red pigment; ruddiness; red wine," mid-13c., from red (adj.1). Compare Old High German roti, German röthe "redness, red," from the adjective in German. As "a person with red hair" from early 14c. In finance, in the red for "overdrawn, losing money" is by 1926, from the color formerly conventional for recording debts and balances in accounts.

Red is one of the most general color-names, and embraces colors ranging in hue from rose aniline to scarlet iodide of mercury and red lead. A red yellower than vermillion is called scarlet; one much more purple is called crimson. A very dark red, if pure or crimson, is called maroon; if brownish, chestnut or chocolate. A pale red — that is, one of low chroma and high luminosity — is called a pink, ranging from rose-pink, or pale crimson, to salmon-pink, or pale scarlet. [Century Dictionary]
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pink (n., adj.)

1570s, common name of Dianthus, a garden plant of various colors; a word of unknown origin. It is perhaps from pink (v.) via the notion of "perforated" (scalloped) petals. Or perhaps it is from Dutch pink "small, narrow" (see pinkie), itself obscure, via the term pinck oogen "half-closed eyes," literally "small eyes," which was borrowed into English (1570s) and may have been used as a name for Dianthus, which sometimes has small dots resembling eyes.

The noun meaning "pale red color, red color of low chroma but high luminosity" is recorded by 1733 (pink-coloured is recorded from 1680s), from one of the common colors of the flowers.  The adjective pink is attested by 1720. As an earlier name for such a color English had incarnation "flesh-color" (mid-14c.), and as an adjective incarnate (1530s), from Latin words for "flesh" (see incarnation) but these also had other associations and tended to drift in sense from "flesh-color, blush-color" toward "crimson, blood color."

The flower meaning led (by 1590s) to a figurative use for "the flower" or highest type or example of excellence of anything (as in Mercutio's "Nay, I am the very pinck of curtesie," Rom. & Jul. II.iv.61). Compare flour (n.). The political noun sense "person perceived as left of center but not entirely radical (i.e. red)" is attested by 1927, but the image dates to at least 1837. Pink slip "discharge notice" is attested by 1915; pink slips had various connotations in employment in the first decade of the 20th century, including a paper signed by a worker to testify he would leave the labor union or else be fired. To see pink elephants "hallucinate from alcoholism" is from 1913 in Jack London's "John Barleycorn."

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dwarf (n.)

Old English dweorh, dweorg (West Saxon), duerg (Mercian), "very short human being, person much below ordinary stature, whether of proportionate parts or not," also "supernatural being of subhuman size," from Proto-Germanic *dweraz (source also of Old Frisian dwerch, Old Saxon dwerg, Old High German twerg, German Zwerg, Old Norse dvergr), perhaps from PIE *dhwergwhos "something tiny," but with no established cognates outside Germanic.

Also used by c. 1200 of an animal or plant much below the ordinary size of its species." The use of dwarf in the Germanic mythological sense, "a diminished and generally deformed being, dwelling in rocks and hills and skilled in working metals," seems to have faded after Middle English and been revived after c. 1770 from German.

Whilst in this and other ways the dwarfs do at times have dealings with mankind, yet on the whole they seem to shrink from man; they give the impression of a downtrodden afflicted race, which is on the point of abandoning its ancient home to new and more powerful invaders. There is stamped on their character something shy and something heathenish, which estranges them from intercourse with christians. They chafe at human faithlessness, which no doubt would primarily mean the apostacy from heathenism. In the poems of the Mid. Ages, Laurin is expressly set before us as a heathen. It goes sorely against the dwarfs to see churches built, bell-ringing ... disturbs their ancient privacy; they also hate the clearing of forests, agriculture, new fangled pounding-machinery for ore. ["Teutonic Mythology," Jakob Grimm, transl. Stallybrass, 1883]

The shift of the Old English guttural at the end of the word to modern -f is typical (compare enough, draft) and begins to appear early 14c. In Middle English it also was dwerþ, dwerke. Old English plural dweorgas became Middle English dwarrows, later leveled down to dwarfs. The use of dwarves for the legendary race was popularized by J.R.R. Tolkien. As an adjective, from 1590s.

The use of giant and dwarf in reference to stars of the highest and lowest luminosity is attested by 1914, said to have been suggested by Danish astronomer Ejnar Hertzsprung, (1873-1967); hence red dwarf (attested by 1922), white dwarf, black dwarf "dead and lightless star" (1966).

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