Online Etymology Dictionary

cosmonaut (n.): 1959, Englishing of Russian kosmonavt, ultimately from Greek kosmos (see cosmos) + nautes "sailor" (see naval).
cosmopolitan (adj.): 1844, from cosmopolite "citizen of the world" (q.v.) on model of metropolitan. The U.S. women's magazine of the same name was first published in 1886. Cosmopolitanism first recorded 1828.
cosmopolite (n.): late 16c., "man of the world; citizen of the world," from Greek kosmopolites "citizen of the world," from kosmos "world" (see cosmos) + polites "citizen" (see politic). In common use 17c. in a neutral sense; it faded out in 18c. but was revived from c. 1800 with a tinge of reproachfulness (opposed to patriot).
cosmos (n.): c. 1200 (but not popular until 1848, as a translation of Humboldt's Kosmos), from Latinized form of Greek kosmos "order, good order, orderly arrangement," a word with several main senses rooted in those notions: The verb kosmein meant generally "to dispose, prepare," but especially "to order and arrange (troops for battle), to set (an army) in array;" also "to establish (a government or regime);" "to deck, adorn, equip, dress" (especially of women). Thus kosmos had an important secondary sense of "ornaments of a woman's dress, decoration" (compare kosmokomes "dressing the hair") as well as "the universe, the world."

Pythagoras is said to have been the first to apply this word to "the universe," perhaps originally meaning "the starry firmament," but later it was extended to the whole physical world, including the earth. For specific reference to "the world of people," the classical phrase was he oikoumene (ge) "the inhabited (earth)." Septuagint uses both kosmos and oikoumene. Kosmos also was used in Christian religious writing with a sense of "worldly life, this world (as opposed to the afterlife)," but the more frequent word for this was aion, literally "lifetime, age."
Cossack (n.): 1590s, from Russian kozak, from Turkish kazak "adventurer, guerilla, nomad," from qaz "to wander." The same Turkic root is the source of the people-name Kazakh and the nation of Kazakhstan.
cosset (v.): 1650s, "to fondle, caress, indulge," from a noun (1570s) meaning "lamb brought up as a pet" (applied to persons from 1590s), perhaps from Old English cot-sæta "one who dwells in a cot." Related: Coseted; coseting. Compare German Hauslamm, Italian casiccio.
cost (n.): c. 1200, from Old French cost (12c., Modern French coût) "cost, outlay, expenditure; hardship, trouble," from Vulgar Latin *costare, from Latin constare, literally "to stand at" (or with), with a wide range of figurative senses including "to cost." The idiom is the same one used in Modern English when someone says something "stands at X dollars" to mean it sells for X dollars. The Latin word is from com- "with" (see com-) + stare "to stand," from PIE root *stā- "to stand" (see stet).
cost (v.): late 14c., from Old French coster (Modern French coûter) "to cost," from cost (see cost (n.)).
cost-effective (adj.): also cost effective, 1967, from cost (n.) + effective.
costa (n.): Spanish costa "coast," from same Latin source as English coast (n.). Used in Britain from 1960s in jocular formations (costa geriatrica, costa del crime, etc.) in imitation of the names of Spanish tourist destinations.
costal (adj.): "pertaining to the ribs," 1630s, from French costal (16c.), from Medieval Latin costalis, from costa "a rib" (see coast (n.)).
costard (n.): late 13c., coster, perhaps from Anglo-French or Old French coste "rib" (from Latin costa "a rib;" see coast (n.)). A kind of large apple with prominent "ribs," i.e. one having a shape more like a green pepper than a plain, round apple. Also applied derisively to "the head." Common 14c.-17c. but limited to fruit-growers afterward.
costermonger (n.): 1510s, "itinerant apple-seller" from coster (see costard) + monger (n.). Sense extended from "apple-seller" to any salesman who plied his wares from a street-cart. Contemptuous use is from Shakespeare ("2 Henry IV"), but reason is unclear.
costive (adj.): c. 1400, from Middle French costivé, from Latin constipatus, past participle of constipare (see constipation).
costly (adj.): late 14c., from cost + -ly (1). Earlier formation with the same sense were costful (mid-13c.), costious (mid-14c.).
costume (n.): 1715, "style of dress," an art term, from French costume (17c.), from Italian costume "fashion, habit," from Latin consuetudinem (nominative consuetudo) "custom, habit, usage." Essentially the same word as custom but arriving by a different etymology. From "customary clothes of the particular period in which the scene is laid," meaning broadened by 1818 to "any defined mode of dress." Costume jewelry is first attested 1933.
costume (v.): 1823, from costume (n.). Related: Costumed; costuming.
cosy (adj.): chiefly British form of cozy.
cot (n.1): "small bed," 1630s, from Hindi khat "couch, hammock," from Sanskrit khatva, probably from a Dravidian source (compare Tamil kattil "bedstead").
cot (n.2): "hut, cottage;" see cote.
cotangent (n.): from co. tangent, abbreviation of complement + tangent (n.).
cote (n.): Old English cote, fem. of cot (plural cotu) "small house, bedchamber, den" (see cottage). Applied to buildings for animals from early 15c.
coterie (n.): 1738, from French coterie "circle of acquaintances," originally in Middle French an organization of peasants holding land from a feudal lord (14c.), from cotier "tenant of a cote" (see cottage).
coterminous (adj.): 1630s, malformed in English from co- + terminous (see terminal). Latin purists prefer conterminous.
cotillion (n.): type of dance, 1766, from French cotillion (15c.), originally "petticoat," a double diminutive of Old French cote "skirt" (see coat (n.)); its application to a kind of dance arose in France and is considered obscure by some linguists, but there are lively turns in the dance that flash the petticoats.

Meaning "formal ball" is 1898, American English, short for cotillion ball. French uses -on (from Latin -onem) to reinforce Latin nouns felt to need more emphatic power (as in poisson from Latin piscis). It also uses -on to form diminutives, often strengthened by the insertion of -ill-, as in the case of this word.
cotquean (n.): 1540s, obsolete, "housewife of a cot," from cot (see cottage) + quean; hence "a vulgar beldam, scold" [OED]; also used contemptuously (by Shakespeare, etc.) of men seen as overly interested in housework.
cottage (n.): late 13c., from Old French cote "hut, cottage" + Anglo-French suffix -age (probably denoting "the entire property attached to a cote"). Old French cot is probably from Old Norse kot "hut," cognate of Old English cot, cote "cottage, hut," from Proto-Germanic *kutan (source also of Middle Dutch cot, Dutch kot).

Meaning "small country residence" (without suggestion of poverty or tenancy) is from 1765. Modern French cottage is a 19c. reborrowing from English. Cottage industry is attested from 1921. Cottage cheese is attested from 1831, American English, earliest in reference to Philadelphia:
There was a plate of rye-bread, and a plate of wheat, and a basket of crackers; another plate with half a dozen paltry cakes that looked as if they had been bought under the old Court House; some morsels of dried beef on two little tea-cup plates: and a small glass dish of that preparation of curds, which in vulgar language is called smear-case, but whose nom de guerre is cottage-cheese, at least that was the appellation given it by our hostess. ["Miss Leslie," "Country Lodgings," Godey's "Lady's Book," July 1831]
cotter (n.): 1640s, perhaps a shortened form of cotterel, a dialectal word for "cotter pin or bolt, bracket to hang a pot over a fire" (1560s), itself of uncertain origin.
cotton (n.): late 13c., from Old French coton (12c.), ultimately (via Provençal, Italian, or Old Spanish) from Arabic qutn, a word perhaps of Egyptian origin. Philip Miller of the Chelsea Physic Garden sent the first cotton seeds to American colony of Georgia in 1732. Also ultimately from the Arabic word, Dutch katoen, German Kattun, Provençal coton, Italian cotone, Spanish algodon, Portuguese algodão. Cotton gin is recorded from 1794 (see gin (n.2)).
cotton (v.): "to get on with" someone (usually with to), 1560s, perhaps from Welsh cytuno "consent, agree." But perhaps also a metaphor from cloth finishing and thus from cotton (n.). Related: Cottoned; cottoning.
cotton-picking (adj.): as a deprecatory term first recorded in a Bugs Bunny cartoon, but a similar noun meaning "contemptible person" dates to around 1919, perhaps with racist overtones that have faded over the years. Before mechanization, cotton picking was the most difficult labor on a cotton plantation.
I drove out to a number of the farms near Denison and found many very young white children working all day in the hot sun picking and dragging sacks of cotton. In one field the labor corps consisted of one woman and six children, one of them 5 years, one 6 years, one 7 years, one 9 years, and two about 11. The father was plowing. The 5 and 6 year olds worked all day as did the rest. The 7-year-old said he picked 50 pounds a day and the 9 year old 75 pounds. (A good picker averages several hundred a day.) School begins late on account of the cotton picking, but the children nearly all prefer school to the picking. Picking hours are long, hot, and deadly monotonous. While the very young children seem to enjoy it, very soon their distaste for it grows into all-absorbing hatred for all work. ["Field Notes of Lewis W. Hine, Child-Labor Conditions in Texas," report to U.S. Congressional Commission on Industrial Relations, 1916]
Cottonian: library in the British Museum, named for antiquarian Sir Robert Bruce Cotton (1570-1631). He donated some book to the state and his grandson donated the rest. It was badly damaged in a fire in 1731. The surname represents Old English cotum, plural of cot "cottage."
cotyledon (n.): from 1540s, in various sense, from Latin cotyledon "pennywort, navelwort," from Greek kotyledon "cup-shaped cavity," from kotyle "hollow thing, small vessel," also the name of a small liquid measure (nearly a half-pint); which is of uncertain origin. Botanical sense is 1776, from Linnaeus (1751).
couch (v.): c. 1300, "to overlay with gold, inlay," from Old French couchier "to lay down, place; go to bed, put to bed," from Latin collocare "to lay, place, station, arrange," from com- "together" (see com-) + locare "to place" (see locate). Meaning "to put into words" is from 1520s. Related: Couched; couching. Heraldic couchant ("lying down with the head up") is late 15c., from the French present participle.
couch (n.): mid-14c., from Old French couche (12c.) "a bed, lair," from coucher "to lie down," from Latin collocare (see couch (v.)). Traditionally, a couch has the head end only raised, and only half a back; a sofa has both ends raised and a full back; a settee is like a sofa but may be without arms; an ottoman has neither back nor arms, nor has a divan, the distinctive feature of which is that it goes against a wall. Couch potato first recorded 1979.
couch-grass (n.): 1570s; the first element is a corruption of Old English cwice (see quick).
cougar (n.): 1774, from French couguar, Buffon's adaption (influenced by jaguar) of a word the Portuguese picked up in Brazil as çuçuarana, perhaps from Tupi susuarana, from suasu "deer" + rana "false." Another proposed source is Guarani guaçu ara. Evidently the cedillas dropped off the word before Buffon got it. Slang sense of "older woman (35-plus) who seeks younger males as sex partners" is attested by 2002; said in some sources to have originated in Canada, probably from some reference to predatory feline nature.
cough (v.): early 14c., coughen, probably in Old English, but not recorded, from Proto-Germanic *kokh-, with the rough "kh" of German or of Scottish loch (source also of Middle Dutch kochen, Middle High German kuchen). Onomatopoeic. Related: Coughed; coughing. As a noun from c. 1300.
could (v.): Old English cuðe, past tense of cunnan "to be able" (see can (v.1)); ending changed 14c. to standard English -d(e). The excrescent -l- was added 15c.-16c. on model of would, should, where it is historical.
couldn't: by 1670s, contraction of could + not.
coulee (n.): "deep ravine, seasonally flooded," 1804, a North American word, originally in areas explored by French trappers, from French coulée "flow" (17c.), from fem. past participle of couler "to flow," from Latin colare "to filter, strain" (see colander).
coulomb (n.): 1881, named for French chemist Charles-Augustin de Coulomb (1736-1806), who devised a method of measuring electrical quantity. It is the quantity of electricity conveyed in 1 second by a current of 1 ampere. The name is a French form of Columbus.
coulrophobia (n.): "morbid fear of clowns," by 2001 (said in Web sites to date from 1990s or even 1980s), a popular term, not from psychology, possibly facetious, though the phenomenon is real enough; said to be built from Greek kolon "limb," with some supposed sense of "stilt-walker," hence "clown" + -phobia.

Ancient Greek words for "clown" were sklêro-paiktês, from paizein "to play (like a child);" or deikeliktas; other classical words used for theatrical clowns were related to "rustic," "peasant" (compare Latin fossor "clown," literally "laborer, digger," related to fossil).

The whole creation looks suspiciously like the sort of thing idle pseudo-intellectuals invent on the Internet and which every smarty-pants takes up thereafter; perhaps it is a mangling of Modern Greek klooun "clown," which is the English word borrowed into Greek.
coulter (n.): Old English culter, from Latin culter "a knife, iron blade in a plowshare," from PIE root *(s)kel- "to cut" (see scale (n.1)). As a surname (13c.), probably from Coulter in Lancashire.
Coumadin (n.): by 1953, name for human anti-coagulant use of the rat poison warfarin sodium, abstracted from the chemical name, 3-(α-acetonylbenzyl)-4-hydroxycoumarin; earlier known as Dicoumarol, it attained publicity when it was used in 1955 to treat U.S. President Dwight Eisenhower after a heart attack. The coumarin element (1830) is from French coumarine, from coumarou, the native name in Guyana of the tonquin bean, one source of the substance.
council (n.): early 12c., from Anglo-French cuncile, from Old North French concilie (Old French concile, 12c.) "assembly; council meeting; body of counsellors," from Latin concilium "a meeting, a gathering of people," from PIE *kal-yo-, from root *kele- (2) "to shout" (see claim (v.)). The notion is of a calling together. Tendency to confuse it in form and meaning with counsel has been consistent since 16c.
councillor (n.): late 14c., alteration of counsellor by assimilation to council.
councilor (n.): see councillor.
counsel (n.): early 13c., from Old French counseil (10c.) "advice, counsel; deliberation, thought," from Latin consilium "plan, opinion" (see consultation). As a synonym for "lawyer," first attested late 14c.
counsel (v.): late 13c., from Old French conseiller "to advise, counsel," from Latin consiliari, from consilium "plan, opinion" (see counsel (n.)). Related: Counseled. Counseling "giving professional advice on social or psychological problems" dates from 1940.