also moon-raker, "stupid or silly person," in England, a name traditionally given to Wiltshire people, 1787, from the stock joke about fools who mistook the reflection of the moon in a pond for a cheese and tried to rake it out. But as told in Wiltshire, the men were surprised trying to rake up kegs of smuggled brandy, and put off the revenuers by acting foolish. Compare moonshine. Related: Moonraking.
early 15c., "moonlight, the shining of the moon," from moon (n.) + shine (n.). Similar formation in Dutch maneschijn, German Mondschein, Swedish månsken, Danish maaneskin. In a figurative use, "appearance without substance, pretense, fiction" from late 15c.; perhaps from the notion of "moonshine in water" (see moonraker) or "light without heat."
Meaning "illicit or smuggled liquor" is attested from 1785 (earliest reference is to that smuggled on the coasts of Kent and Sussex; in reference to Southern U.S., by 1829), from the notion of being brought in or taken out under cover of darkness at night. Moonlight also occasionally was used in this sense early 19c. As a verb in this sense from 1883. Related: Moonshiner "smuggler; one who pursues a dangerous or illegal trade at night" (1860).
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]