Online Etymology Dictionary

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" (cf. 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 "group of people, meeting," from com- "together" (see com-) + calare "to call" (see claim (v.)). 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.
counsellor (n.): early 13c., from Old French conseillier (Modern French conseiller), from Latin consilator, agent noun from consiliare, from consilium (see counsel (v.)). Meaning "one who gives professional legal advice" is from 1530s. Psychological sense (marriage counsellor, etc., is from 1940).
counselor (n.): see counsellor.
count (v.): mid-14c., from Old French conter "add up," but also "tell a story," from Latin computare (see compute). Related: Counted; counting. Modern French differentiates compter "to count" and conter "to tell," but they are cognates.
count (n.): title of nobility, c.1300, from Anglo-French counte (Old French conte), from Latin comitem (nominative comes) "companion, attendant," the Roman term for a provincial governor, from com- "with" (see com-) + stem of ire "to go" (see ion). The term was used in Anglo-French to render Old English eorl, but the word was never truly naturalized and mainly was used with reference to foreign titles.
countdown (n.): 1953, American English, in early use especially of launches of rockets or missiles, from count (v.) + down.
countenance (v.): late 15c., "to behave or act," from countenance (n.). Sense of "to favor, patronize" is from 1560s, from notion of "to look upon with sanction or smiles." Related: Countenanced; countenancing.
countenance (n.): mid-13c., from Old French contenance "demeanor, bearing, conduct," from Latin continentia "restraint, abstemiousness, moderation," literally "way one contains oneself," from continentem, present participle of continere (see contain). Meaning evolving Middle English from "appearance" to "facial expression betraying a state of mind," to "face" itself (late 14c.).
counter (n.): mid-14c., "table where a money lender does business," from Old French contouer, comptoir (14c.) "counting room, table of a bank," from Medieval Latin computatorium "place of accounts," from Latin computatus, past participle of computare (see compute). Generalized 19c. from banks to shops, then extended to display cases for goods. Phrase under the counter is from 1926.
counter (v.): "go against," late 14c., from Old French countre "facing opposite" (see counter-). Related: Countered; countering. As an adverb, from mid-15c.; as an adjective, from 1590s.
Counter Reformation: 1840, from counter- + Reformation.
counter-: word-forming element meaning "against; in return; corresponding," from Anglo-French countre-, French contre-, from Latin contra "opposite, contrary to, against, in return," also used as a prefix (see contra-).
counteract (v.): 1670s, from counter- + act (v.). Related: Counteracted; counteracting.
counterargument (n.): 1862, from counter- + argument.
counterattack (n.): also counter-attack, 1882, from counter- + attack (n.); as two words from early 19c. The verb is recorded from 1916.
counterbalance (v.): 1570s, from counter- + balance (v.), in reference to scales. Figurative use dates from 1630s. As a noun, from c.1600.
counterclockwise (adj., adv.): 1870, also counter-clockwise; from counter- + clockwise.
counterculture (n.): also counter-culture, counter culture, 1968, from counter- + culture (q.v.).
counterfactual (adj.): 1946, from counter- + factual.
counterfeit (v.): late 13c., from Old French contrefait "imitated" (Modern French contrefait), past participle of contrefaire "imitate," from contre- "against" (see contra-) + faire "to make, to do" (from Latin facere; see factitious). Medieval Latin contrafactio meant "setting in opposition or contrast." Related: Counterfeited; counterfeiting. The noun and adjective are from late 14c.
counterinsurgency (n.): 1962, from counter- + insurgency.
counterintelligence (n.): also counter-intelligence, 1940, from counter- + intelligence.
counterintuitive (adj.): also counter-intuitive, 1955, from counter- + intuitive.
countermand (v.): early 15c., from Old French contremander "reverse an order or command" (13c.), from contre- "against" (see contra-) + mander, from Latin mandare "to order" (see mandate (n.)). Related: Countermanded; countermanding.
countermeasure (n.): 1923, from counter- + measure (n.).
counteroffer (n.): 1788, from counter- + offer (n.).
counterpane (n.): "outer covering of a bed," c.1600, alteration of earlier counterpoynte (mid-15c.; see counterpoint) on model of Middle French pan, Latin pannus "cloth" (see pane).
counterpart (n.): mid-15c., originally countre part "duplicate of a legal document," from Middle French contrepartie, from contre "facing, opposite" (see contra-) + partie "copy of a person or thing," originally fem. past participle of partir "to divide" (see party (n.)).
counterpoint (n.): early 15c., of stitching, from Old French cuilte contrepointe "quilt stitched through and through," altered from coute pointe, from Medieval Latin culcita puncta "quilted mattress," from Latin culcita "cushion" + puncta, fem. past participle of pungere "to prick, stab" (see pungent).

Of music, mid-15c., from Old French contrepoint, from Medieval Latin cantus contrapunctus, from contrapunctum, from Latin contra + puncta, with reference to the indication of musical notes by "pricking" with a pointed pen over or under the original melody on a manuscript.
counterpoise (n.): early 15c., from Old French contrepois (Modern French contrepoids), from contre- "against" (see contra-) + peis, from Latin pensum "weight," noun use of neuter past participle of pendere "to weigh" (see pendant).
counterproductive (adj.): also counter-productive, counter productive, 1920, American English, from counter- + productive.
counterrevolution (n.): also counter-revolution, 1791, from counter- + revolution. First recorded in U.S. with reference to American Revolution.
countersign (n.): 1590s, from Middle French contresigne, from contre- "against" (see contra-) + signe "sign" (see sign (n.)).
countertop (n.): 1878, from counter (n.) + top (n.1).
countervail (v.): late 14c., "to be worth as much as," also "to prevail against," from Anglo-French countrevaloir, Old French contrevaloir "to be effective against, be comparable to," from Latin phrase contra valere "to be worth against" (see contra- and valiant). Related: Countervailing.
countess (n.): mid-12c., adopted in Anglo-French for "the wife of an earl," from Medieval Latin cometissa, fem. of Latin comes "count" (see count (n.)).
countless (adj.): "numberless, uncountable," 1580s, from count (v.) + -less.
countrified (adj.): 1650s, from country + past participle form of -fy.
country (n.): mid-13c., "district, native land," from Old French contree, from Vulgar Latin *(terra) contrata "(land) lying opposite," or "(land) spread before one," from Latin contra "opposite, against" (see contra-). Sense narrowed 1520s to rural areas, as opposed to cities. Replaced Old English land. As an adjective from late 14c. First record of country-and-western music style is from 1942. Country club first recorded 1886. Country mile "a long way" is from 1915, American English.
countryman (n.): late 13c., from country + man (n.).
countryside (n.): mid-15c., literally "one side of a country" (a valley, a mountain range, etc.), from country + side (n.); hence, "any tract of land having a natural unity" (1727).
county (n.): c.1300, from Anglo-French counte, from Late Latin comitatus "jurisdiction of a count," from Latin comes (see count (n.)); replaced Old English scir "shire."