Etymology
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dark (adj.)
Origin and meaning of dark

Middle English derk, later dark, from Old English deorc "without light, lacking light or brightness (especially at night), obscure, gloomy;" figuratively "sad, cheerless; sinister, wicked," from Proto-Germanic *derkaz (source also of Old High German tarchanjan "to hide, conceal"), which is of uncertain etymology. For vowel change, see marsh.

Application to colors, "not radiating or reflecting much light," is from late 14c. Of complexion, "not fair," from early 14c. Figurative sense of "obscure, not easily understood" is from early 13c.; that of "sullen, sad" is from 1590s. Meaning "concealed, secret" is from late 14c. Dark Continent "Africa" (1828) combines several figurative senses (earliest references are in missionary publications). Theater slang for "closed" is from 1916.

Dark Ages "benighted time in history, period of ignorance" is attested by 1739; the specific focus on the centuries of the early Middle Ages in Europe, from the fall of Rome to the revival of secular literature, is from 1830s, from dark in a sense of "characterized by ignorance, backward in learning, void of intellectual light" (late 14c.). 

Dark horse "competitor for honors or office about whom nothing certain is known, or whose identity is at first concealed," especially, in U.S., politics, "one who is unexpectedly brought forward as a candidate in a convention," 1842, is an image from horse racing, of horses whose performances or capabilities are not generally known, in which dark is used in its figurative sense of "unknown."

Moonraker is called a "dark horse"; that is neither his sire nor dam is known. ["Pierce Egan's Book of Sports," London, 1832] 
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matter (n.)

c. 1200, materie, "the subject of a mental act or a course of thought, speech, or expression," from Anglo-French matere, Old French matere "subject, theme, topic; substance, content; character, education" (12c., Modern French matière) and directly from Latin materia "substance from which something is made," also "hard inner wood of a tree." According to de Vaan and Watkins, this is from mater "origin, source, mother" (see mother (n.1)). The sense developed and expanded in Latin in philosophy by influence of Greek hylē (see hylo-) "wood, firewood," in a general sense "material," used by Aristotle for "matter" in the philosophical sense. 

The Latin word also is the source of Spanish, Portuguese, and Italian materia, Dutch, German, and Danish materie, vernacular Spanish madera, Portuguese madeira "wood" (compare Madeira). The Middle English word also sometimes was used specifically as "piece of wood."

From c. 1200 as "a subject of a literary work, content of what is written, main theme;" sense of "narrative, tale, story" is from c. 1300. Meaning "physical substance generally" is from mid-14c.; that of "substance of which some specific object is or may be composed" is attested from late 14c. Meaning "piece of business, affair, activity, situation; subject of debate or controversy, question under discussion" is from late 14c. In law, "something which is to be tried or proved," 1530s.

Matter of course "something expected" attested from 1739 (adjectival phrase matter-of-course "proceeding as a natural consequence" is by 1840). For that matter "as far as that goes, as far as that is concerned" is attested from 1670s. What is the matter "what concerns (someone), what is the cause of the difficulty" is attested from mid-15c., from matter in the sense of "circumstance or condition as affecting persons and things." To make no matter to "be no difference to" also is mid-15c., with matter in the meaning "importance, consequence."

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dark (n.)
Origin and meaning of dark

early 13c., derk, "absence of light, night-time," from dark (adj.). Figurative in the dark "in a state of ignorance" is from 1670s; earlier it meant "in secrecy, in concealment" (late 14c.).

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matter (v.)
"to be of importance or consequence," 1580s, from matter (n.). Related: Mattered; mattering.
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dark-room (n.)

also darkroom, in photography, "room from which any light that would affect a photographic plate or film has been excluded," 1841, from dark (adj.) + room (n.).

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matter-of-fact (adj.)

"consisting of or pertaining to facts, not fanciful or ideal," 1712, from the noun phrase matter of fact "reality as distinguished from what is fanciful or hypothetical, truth attested by direct observation or authentic testimony," which is originally a legal term (1570s, translating Latin res facti), "that which is fact or alleged fact; that portion of an inquiry concerned with the truth or falsehood of alleged facts, subject of discussion belonging to the realm of fact" (as distinguished from matter of inference, opinion, law, etc.). See matter (n.) + fact.

The meaning "prosaic, unimaginative, adhering to facts" is from 1787. Related: Matter-of-factly; matter-of-factness. German Tatsache is said to be a loan-translation of the English word.

In law, that which is fact or alleged as fact; in contradistinction to matter of law, which consists in the resulting relations, rights, and obligations which the law establishes in view of given facts. Thus, the questions whether a man executed a contract, and whether he was intoxicated at the time, relate to matters of fact; whether, if so, he is bound by the contract, and what the instrument means, are matters of law. [Century Dictionary]
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dye (n.)

"coloring matter in solution," Middle English deie, from Old English deah, deag "a color, hue, tinge," from Proto-Germanic *daugo (source also of Old Saxon dogol "secret," Old High German tougal "dark, hidden, secret," Old English deagol "secret, hidden; dark, obscure," dohs, dox "dusky, dark").

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darksome (adj.)

"somewhat dark, gloomy, shadowy," 1520s; see dark (adj.) + -some.

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fuscous (adj.)
"dark-colored, of brown tinged with gray," 1660s, from Latin fuscus "dark, swarthy, dark-skinned" (see dusk). Earlier as fusc, fusk (1560s).
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Pismo Beach 

place in California; according to Bright, the name is Obsipeño (Chumashan) /pismu'/ "tar, asphalt," literally "the dark stuff," from /piso'/ "to be black, dark."

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