Online Etymology Dictionary

cock-a-doodle-doo: 1570s, imitative; cf. French cocorico, German kikeriki, Latin cucurire, Russian kikareku, Vietnamese cuc-cu, Arabic ko-ko, etc.
cockade (n.): 1709, earlier cockard (1650s), from French cocarde (16c.), fem. of cocard (Old French cocart) "foolishly proud, cocky," as a noun, "idiot, fool;" an allusive extension from coq (see cock (n.1)).
Cockaigne (n.): c.1300, from Old French Cocaigne (12c.) "lubberland," imaginary country, abode of luxury and idleness. Of obscure origin, speculation centers on words related to cook (v.) and cake (cf. Middle Dutch kokenje, a child's honey-sweetened treat; also cf. Big Rock Candy Mountain). The German equivalent is Schlaraffenland.
cockamamie (adj.): American English slang word attested by 1946, popularized c.1960, but said to be New York City children's slang from mid-1920s; perhaps an alteration of decalcomania (see decal).
cockatoo (n.): 1610s, from Dutch kaketoe, from Malay kakatua, possibly echoic, or from kakak "elder brother or sister" + tua "old." Also cockatiel (1880), from Dutch diminutive kaketielje (1850), which is perhaps influenced by Portuguese. Spelling influenced by cock (n.1).
cockatrice (n.): late 14c., from Old French cocatriz, altered (by influence of coq) from Late Latin *calcatrix, from Latin calcare "to tread" (from calx (1) "heel"), as translation of Greek ikhneumon, literally "tracker, tracer."

In classical writings, an Egyptian animal of some sort, the mortal enemy of the crocodile, which it tracks down and kills. This vague sense became hopelessly confused in the Christian West, and in England the word ended up applied to the equivalent of the basilisk. A serpent hatched from a cock's egg, it was fabled to kill by its glance and could be slain only by tricking it into seeing its own reflection. Belief in them persisted even among the educated because the word was used in the KJV several times to translate a Hebrew word for "serpent." In heraldry, a beast half cock, half serpent.
cockchaffer (n.): from cock (n.1), in reference to its size, + chaffer.
cockerel (n.): "young cock," mid-15c. (late 12c. as a surname), apparently a diminutive of cock (n.1). Despite the form, no evidence that it is from French.
cockeyed (adj.): 1821, "squint-eyed," perhaps from cock (v.) in some sense + eye (n.). Figurative sense of "absurd, askew, crazy" is from 1896; that of "drunk" is attested from 1926.
cockle (n.1): type of mollusk, early 14c., from Old French coquille (13c.) "scallop, scallop shell; mother of pearl; a kind of hat," altered (by influence of coque "shell") from Vulgar Latin *conchilia, from Latin conchylium "mussel, shellfish," from Greek konkhylion "little shellfish," from konkhe "mussel, conch." Phrase cockles of the heart (1660s) is perhaps from similar shape, or from Latin corculum, diminutive of cor "heart."
cockle (n.2): flowering weed that grows in wheat fields, Old English coccel "darnel," used in Middle English to translate the Bible word now usually given as tares (see tare (n.1)). It is in no other Germanic language and may be from a diminutive of Latin coccus "grain, berry."
cockney (n.): c.1600, usually said to be from rare Middle English cokenei, cokeney "spoiled child, milksop" (late 14c.), originally cokene-ey "cock's egg" (mid-14c.). Most likely disentangling of the etymology is to start from Old English cocena "cock's egg" -- genitive plural of coc "cock" + æg "egg" -- medieval term for "runt of a clutch," extended derisively c.1520s to "town dweller," gradually narrowing thereafter to residents of a particular neighborhood in the East End of London. Liberman, however, disagrees:
[I]n all likelihood, not the etymon of ME cokeney 'milksop, simpleton; effeminate man; Londoner,' which is rather a reshaping of [Old French] acoquiné 'spoiled' (participle). However, this derivation poses some phonetic problems that have not been resolved.
The accent so called from 1890, but the speech peculiarities were noted from 17c. As an adjective in this sense, from 1630s.
cockpit (n.): 1580s, "a pit for fighting cocks," from cock (n.1) + pit (n.1). Used in nautical sense (1706) for midshipmen's compartment below decks; transferred to airplanes (1914) and to cars (1930s).
cockroach (n.): 1620s, folk etymology (as if from cock + roach) of Spanish cucaracha "chafer, beetle," from cuca "kind of caterpillar." Folk etymology also holds that the first element is from caca "excrement."
A certaine India Bug, called by the Spaniards a Cacarootch, the which creeping into Chests they eat and defile with their ill-sented dung [Capt. John Smith, "Virginia," 1624].
cockscomb (n.): c.1400, "comb or crest of a cock," from possessive of cock (n.1) + comb (n.). Meaning "cap worn by a professional fool" is from 1560s; hence "conceited fool" (1560s), a sense passing into the derivative coxcomb. As a plant name, from 1570s.
cocksucker (n.): 1890s, "one who does fellatio" (especially a male homosexual); 1920s as "contemptible person," American English, from cock (n.1) in phallic sense + sucker (n.). Used curiously for aggressively obnoxious men; the ancients would have recoiled at this failure to appreciate the difference between passive and active roles; Catullus, writing of his boss, employs the useful Latin insult irrumator, which means "someone who forces others to give him oral sex," hence "one who treats people with contempt."
cocksure (adj.): 1520s, "certain," from cock (n.1) + sure (adj.). Probably "as assured as a cock." "The word was originally perfectly dignified, and habitually used in the most solemn connexions" [OED].
cocktail (n.): first attested 1806; H.L. Mencken lists seven versions of its origin, perhaps the most persuasive is French coquetier "egg-cup" (15c.; in English cocktay). In New Orleans, c.1795, Antoine Amédée Peychaud, an apothecary (and inventor of Peychaud bitters) held Masonic social gatherings at his pharmacy, where he mixed brandy toddies with his own bitters and served them in an egg-cup. On this theory, the drink took the name of the cup. Used from 1920s of any mix of substances (e.g. fruit, Molotov). Cocktail party first attested 1928.
cocky (adj.): "arrogantly pert," 1768; originally "lecherous" (1540s); from cock (n.1) + -y (2). Related: Cockiness.
coco (n.): "palm tree," mid-16c., from Spanish and Portuguese coco "grinning face," on resemblance of the three holes at the base of the shell to a human face. The earlier word for it was the Latinized form cocus, which sometimes was anglicized as cocos.
cocoa (n.): powder from cacao seeds, 1707, corruption (by influence of coco) of cacao. The printing of Johnson's dictionary ran together the entries for coco and cocoa, fostering a confusion that never has been undone.
coconut (n.): 1610s, from coco + nut. Meaning "the head" is slang from 1834.
cocoon (n.): 1690s, from Middle French coucon (16c., Modern French cocon), from coque "clam shell, egg shell, nut shell" (7c.), from Old French coque "shell," from Latin coccum "berry," from Greek kokkos "berry, seed" (see cocco-). The sense of "one's interior comfort place" is from 1986. Also see -oon.
cocoon (v.): 1986, "to stay inside and be inactive," from coccoon (n.).
A lady with an enchanting name, Faith Popcorn, has identified a menacing new American behavior that she gives the sweet name of 'cocooning.' It threatens the nation's pursuit of happiness, sometimes called the economy. [George Will, April 1987]
Related: Cocooned; cocooning.
cocotte (n.): type of cooking vessel, 1907, from French cocotte "saucepan" (19c.), a diminutive from cocasse, ultimately from Latin cucama. Sense of "prostitute," 1867, is from French cocotte, originally a child's name for "little hen" (18c.), hence "sweetie, darling."
cod (n.): large sea fish, mid-14c. (late 13c. in a surname, Thomas cotfich), of unknown origin; despite similarity of form it has no conclusive connection to the widespread Germanic word for "bag" (e.g. Old English codd, preserved in codpiece). Cod-liver oil known since at least 1610s, was recommended medicinally since 1783, but not popular as a remedy until after 1825.
coda (n.): "concluding passage in a musical composition," 1753, from Latin cauda "tail of an animal."
coddle (v.): c.1600, "boil gently," probably from caudle "warm drink for invalids" (c.1300), from Anglo-French caudel (c.1300), ultimately from Latin calidium "warm drink, warm wine and water," neuter of calidus "hot," from calere "be warm" (see calorie). Verb meaning "treat tenderly" first recorded 1815 (in Jane Austen's "Emma"). Related: Coddled; coddling.
code (n.): c.1300, "systematic compilation of laws," from Old French code "system of laws, law-book" (13c.), from Latin codex, earlier caudex "book, book of laws," literally "tree trunk," hence, book made up of wooden tablets covered with wax for writing. Meaning "cipher" (the sense in secret code) is from 1808.
code (v.): 1815, from code (n.). Specifically in the computer sense from 1947. Related: Coded; coding.
codec (n.): by 1970, an abbreviation from compressor-decompressor or coder-decoder, on model of modem.
codefendant (n.): also co-defendant, 1640s, from co- + defendant.
codeine (n.): alkaloid present in opium, 1838, from French codéine, coined, with chemical suffix -ine (2), from Greek kodeia "poppy head," related to kooz "prison," literally "hollow place;" kodon "bell, mouth of a trumpet;" koilos "hollow," from PIE root *kel- (see cell). Originally codeina; modern form is from 1881.
codependent (adj.): also co-dependent, by 1905, in various senses, from co- + dependent. Modern psycological sense is attested from c.1983. Related: Codependence, codependency.
codex (n.): "manuscript volume (especially an ancient one)," 1845, from Latin codex (see code (n.)).
codger (n.): 1756, probably a variant of cadger "beggar" (see cadge (v.)), which is of unknown origin.
codicil (n.): early 15c., from Middle French codicille, from Latin codicillus "a short writing, a small writing tablet," dimibnutive of codex (genitive codicis), see code (n.).
codify (v.): c.1800, from code (n.) + -fy. Related: codified; codifying; codification.
codominant (adj.): also co-dominant, 1926, from co- + dominant.
codon (n.): 1962, from code (n.) + -on.
codpiece (n.): mid-15c., "a bagged appendage to the front of the breeches; often conspicuous" [OED], from Old English codd "a bag, pouch, husk," in Middle English, "testicles" (common Germanic, cf. Old Norse koddi "pillow," Dutch kodde "bag") + piece (n.).
codswallop (n.): said to be from 19c. (but first attested 1963), perhaps from wallop, British slang for "beer," and cod in one of its various senses, perhaps "testicles."
coe (n.): "hut built over a mine shaft," 1650s, from some source akin to Dutch kouw, German kaue in the same sense, from West Germanic *kauja-, an early borrowing of Latin cavea "hollow," from cavus "a hollow" (see cave (n.)).
coeducational (adj.): also co-educational, 1881, from co-education (1852), from co- + education.
coefficient (n.): also co-efficient, c.1600, from co- + efficient. Probably influenced by Modern Latin coefficiens, which was used in mathematics in 16c., introduced by French mathematician François Viète (1540-1603). As an adjective from 1660s.
coelacanth (n.): 1857, from Modern Latin Coelacanthus (genus name, 1839, Agassiz), from Greek koilos "hollow" (from PIE root *kel-; see cell) + akantha "spine" (see acrid). So called from the hollow fin rays supporting the tail. Known only as a fossil, the most recent one from 70 million years ago, until discovered living in the sea off the east coast of South Africa Dec. 22, 1938. The specimen was described by Marjorie Courtney-Latimer, who wrote about it to S.African ichthyologist J.L.B. Smith.
I stared and stared, at first in puzzlement. I did not know any fish of our own, or indeed of any seas like that; it looked more like a lizard. And then a bomb seemed to burst in my brain, and beyond that sketch and the paper of the letter, I was looking at a series of fishy creatures that flashed up as on a screen, fishes no longer here, fishes that had lived in dim past ages gone, and of which only fragmentary remains in rock are known. [J.L.B. Smith, "Old Fourlegs: The Story of the Coelacanth," 1956]
coeliac (adj.): 1660s, from Latin coeliacus, from Greek koiliakos "pertaining to the bowels," also "pain in the bowels," from koilia "bowels, abdominal cavity, intestines, tripe" from koilos "hollow," from PIE root *keue- "to swell; vault, hole" (see cumulus).
coelomate (n.): 1883, from Coelomata (1877), from Modern Latin neuter plural of coelomatus, from Greek koilomat- "hollow, cavity," from PIE root *kel- (see cell).
coeno-: word-forming element meaning "common," Latinized from Greek koinos "common, public, shared, general, ordinary," from PIE *kom "beside, near, by, with" (see com-).
coequal (adj.): late 14c.; see co- + equal.