Online Etymology Dictionary

caste (n.): 1550s, "a race of men," from Latin castus "chaste," from castus "cut off, separated; pure" (via notion of "cut off" from faults), past participle of carere "to be cut off from" (and related to castration), from PIE *kas-to-, from root *kes- "to cut" (cf. Latin cassus "empty, void"). Originally spelled cast in English and later often merged with cast (n.) in its secondary sense "sort, kind, style."

Application to Hindu social groups was picked up by English in India 1610s from Portuguese casta "breed, race, caste," earlier casta raça, "unmixed race," from the same Latin word. The current spelling of of the English word is from this reborrowing. Caste system is first recorded 1840.
castellan (n.): late 14c., from Old North French castelain (Modern French châtelaine; see chatelaine).
castellated (adj.): "furnished with turrets and battlements," 1670s, from Medieval Latin castellatus "built like a castle," past participle of castellare "to fortify as a castle," from Latin castellum "fort" (see castle (n.)). Related: Castellation.
caster (n.1): "person or thing that casts," late 14c. (also sometimes castor), agent noun from cast (v.). Meaning "pepper shaker, small perforated container" is from 1670s, on notion of "throwing."
caster (n.2): "wheel and swivel attached to furniture," 1748, agent noun from cast (v.) in the old sense of "turn." Also sometimes castor.
castigate (v.): c.1600, from Latin castigatus, past participle of castigare "to correct, set right; purify; chastise, punish," from castus "pure" (see caste) + agere "to do" (see act (n.)). The notion behind the word is "make someone pure by correcting or reproving him."
If thou didst put this soure cold habit on To castigate thy pride, 'twere well. [Shakespeare, "Timon" IV.iii (1607)]
Related: Castigated; castigating; castigator; castigatory.
castigation (n.): late 14c., castigacioun, from Latin castigationem (nominative castigatio) "a correcting, reproof, chastizing," noun of action from past participle stem of castigare (see castigate).
Castile: medieval Spanish county and later kingdom, from Vulgar Latin castilla, from Latin castella, plural of castellum "castle, fort, citadel, stronghold" (see castle (n.)); so called in reference to the many fortified places there during the Moorish wars. The name in Spanish is said to date back to c.800. Related: Castilian. As a fine kind of soap, in English from 1610s.
casting (n.): c.1300, "a throwing; late 14c., "a metal casting, a product of a cast;" verbal noun from cast (v.). Theatrical sense is from 1814. Casting couch in the naughty-Hollywood sense is from 1948.
castle (n.): late Old English castel "village" (this sense from a biblical usage in Vulgar Latin); later "large fortified building, stronghold," in this sense from Old North French castel (Old French chastel, 12c.; Modern French château), from Latin castellum "a castle, fort, citadel, stronghold; fortified village," diminutive of castrum "fort," from Proto-Italic *kastro- "part, share;" cognate with Old Irish cather, Welsh caer "town" (and perhaps related to castrare via notion of "cut off;" see caste). In early bibles, castle was used to translate Greek kome "village."

This word also had come to Old English as ceaster and formed the -caster and -chester in place names. Spanish alcazar "castle" is from Arabic al-qasr, from Latin castrum. Castles in Spain translates 14c. French chastel en Espaigne (the imaginary castles sometimes stood in Brie, Asia, or Albania) and probably reflects the hopes of landless knights to establish themselves abroad. The statement that an (English) man's home is his castle is from 16c.
castle (v.): move in chess, recorded under this name from 1650s, from castle (n.), as an old alternative name for the rook, one of the pieces moved. Related: Castled; castling.
castor (n.): late 14c., "beaver," from Old French castor (13c.), from Latin castor "beaver," from Greek Kastor, literally "he who excels," name of one of the divine twins (with Pollux), worshipped by women in ancient Greece as a healer and preserver from disease.

His name was given to secretions of the animal (Latin castoreum), used medicinally in ancient times. (Through this association his name replaced the native Latin word for "beaver," which was fiber.) In English, castor is attested in this sense from c.1600. Modern castor oil is first recorded 1746; it is made from seeds of the plant Ricinus communis but supposedly possesses laxative qualities (and taste) similar to those of beaver juice, and thus so named.
castrate (v.): 1610s (implied in castrated), back-formation from castration (q.v.), or from Latin castratus, past participle of castrare. The figurative sense is attested earlier (1550s). Related: Castrating.
castrati (n.): plural of castrato.
castration (n.): early 15c., castracioun, from Latin castrationem (nominative castratio), noun of action from past participle stem of castrare "to castrate, emasculate," supposedly from a noun *castrum "knife, instrument that cuts," from PIE root *kes- "to cut" (see caste). Freud's castration complex is attested from 1914 in English (translating German Kastrationsangst).
castrato (n.): 1763, from Italian castrato, from Latin castratus (see castration).
casual (adj.): late 14c., "subject to or produced by chance," from Middle French casuel (15c.), from Late Latin casualis "by chance," from Latin casus "chance, occasion, opportunity; accident, event" (see case (n.1)).

Of persons, in the sense of "not to be depended on, unmethodical," it is attested from 1883; meaning "showing lack of interest" is from 1916. Of clothes, "informal," from 1939. Related: Casually.
casualness (n.): 1730, from casual (adj.) + -ness.
casualty (n.): early 15c., "chance, accident; incidental charge," from casual (adj.) on model of royalty, penalty, etc. Casuality had some currency 16c.-17c. but is now obsolete. Meaning "losses in numbers from a military or other troop" is from late 15c. Meaning "an individual killed, wounded, or lost in battle" is from 1844.
casuist (n.): c.1600, "one who studies and resolves cases of conscience," from French casuiste (17c.) or Spanish casuista (the French word also might be from Spanish), Italian casista, all from Latin casus (see case (n.1)) in its Medieval Latin sense "case of conscience." Often since 17c. in a sinister or contemptuous sense. Related: Casuistic; casuistical; casuistically; casuistry.
Casuistry ... destroys, by distinctions and exceptions, all morality, and effaces the essential difference between right and wrong. [Bolingbroke, 1736]
casus belli (n.): 1849, from Latin casus "case" (see case (n.1)) + belli, genitive of bellum "war" (see bellicose). An act justifying war.
cat (n.): Old English catt (c.700), from West Germanic (c.400-450), from Proto-Germanic *kattuz (cf. Old Frisian katte, Old Norse köttr, Dutch kat, Old High German kazza, German Katze), from Late Latin cattus.

The near-universal European word now, it appeared in Europe as Latin catta (Martial, c.75 C.E.), Byzantine Greek katta (c.350) and was in general use on the continent by c.700, replacing Latin feles. Probably ultimately Afro-Asiatic (cf. Nubian kadis, Berber kadiska, both meaning "cat"). Arabic qitt "tomcat" may be from the same source. Cats were domestic in Egypt from c.2000 B.C.E., but not a familiar household animal to classical Greeks and Romans. The nine lives have been proverbial since at least 1560s.

The Late Latin word also is the source of Old Irish and Gaelic cat, Welsh kath, Breton kaz, Italian gatto, Spanish gato, French chat (12c.). Independent, but ultimately from the same source are words in the Slavic group: Old Church Slavonic kotuka, kotel'a, Bulgarian kotka, Russian koška, Polish kot, along with Lithuanian kate and non-Indo-European Finnish katti, which is from Lithuanian.

Extended to lions, tigers, etc. c.1600. As a term of contempt for a woman, from early 13c. Slang sense of "prostitute" is from at least c.1400. Slang sense of "fellow, guy," is from 1920, originally in U.S. Black English; narrower sense of "jazz enthusiast" is recorded from 1931.

Cat's paw (1769, but cat's foot in the same sense, 1590s) refers to old folk tale in which the monkey tricks the cat into pawing chestnuts from a fire; the monkey gets the nuts, the cat gets a burnt paw. Cat bath "hurried or partial cleaning" is from 1953. Cat burglar is from 1907, so called for stealth. Cat-witted "small-minded, obstinate, and spiteful" (1670s) deserved to survive. For Cat's meow, cat's pajamas, see bee's knees.
CAT: 1975, medical acronym for computerized axial tomography or something like it. Related: CAT scan.
cat-o'-nine-tails (n.): 1690s, probably so called in reference to its "claws." It was a legal instrument of punishment in British Navy until 1881.
cata-: word-forming element from Latinized form of Greek kata-, before vowels kat-, from kata "down from, down to." Its principal sense is "down," but occasionally it has senses of "against" (catapult)or "wrongly" (catachresis). Also sometimes used as an intensive or with a sense of completion of action (catalogue). Very active in ancient Greek, this prefix is found in English mostly in words borrowed through Latin after c.1500.
catabolic (adj.): 1876; see catabolism + -ic.
catabolism (n.): 1876, katabolism, "destructive metabolism," from Greek katabole "a throwing down" (also "a foundation"), from kataballein "to throw down," from kata- "down" (see cata-) + ballein "to throw" (see ballistics). Barnhart says probably formed in English on the model of metabolism. Spelling Latinized from 1889.
catachresis (n.): 1580s, from Latin catachresis, from Greek katakhresis "misuse" (of a word), from katakhresthai "to misuse," from kata- "down" (here with a sense of "perversion;" see cata-) + khresthai "to use" (see hortatory). Related: Catachrestic; catachrestical; catachrestically.
cataclysm (n.): 1630s, from French cataclysme (16c.), from Latin cataclysmos or directly from Greek kataklysmos "deluge, flood, inundation," from kataklyzein "to deluge," from kata "down" (see cata-) + klyzein "to wash," from PIE *kleue- "to wash, clean" (see cloaca).
cataclysmic (adj.): 1837, from cataclysm + -ic. Related: Cataclysmical (1857); cataclysmically.
catacomb (n.): usually catacombs, from Old English catacumbas, from Late Latin (400 C.E.) catacumbae (plural), originally the region of underground tombs between the 2nd and 3rd milestones of the Appian Way (where the bodies of apostles Paul and Peter, among others, were said to have been laid), origin obscure, perhaps once a proper name, or dissimilation from Latin cata tumbas "at the graves," from cata- "among" + tumbas. accusative plural of tumba "tomb" (see tomb).

If so, the word perhaps was altered by influence of Latin -cumbere "to lie." From the same source are French catacombe, Italian catacomba, Spanish catacumba. Extended by 1836 in English to any subterranean receptacle of the dead (as in Paris). Related: Catacumbal.
catafalque (n.): 1640s, from French catafalque (17c.), from Italian catafalco "scaffold," from Vulgar Latin *catafalicum, from Greek kata- "down" (see cata-), used in Medieval Latin with a sense of "beside, alongside" + fala "scaffolding, wooden siege tower," a word said to be of Etruscan origin. The Medieval Latin word also yielded Old French chaffaut, chafaud (Modern French échafaud) "scaffold."
Catalan (adj.): "pertaining to Catalonia," also as a noun, "person from Catalonia," late 15c., from the indigenous name, which is of Celtic origin and probably means "chiefs of battle." As a noun meaning "a Catalan," Middle English used Catelaner (mid-14c.), Catellain (early 15c., from French). As a language name in English by 1792. Related: Catalonian (1707).
catalectic (adj.): 1580s, "wanting a syllable in the last foot," from Late Latin catalecticus, from Greek katalektikos "leaving off," from kata- "down" (see cata-) + legein "to leave off, cease from," from PIE *(s)leg- "to be slack, be languid" (see lax).
catalepsy (n.): late 14c., cathalempsia, from Medieval Latin catalepsia, from Late Latin catalepsis, from Greek katalepsis "a seizure, a seizing upon, a taking possession," from kataleptos "seized," from katalambanein "to seize upon," from kata- "down" (see cata-) + lambanein "to take" (see analemma).
cataleptic (adj.): 1680s, from Late Latin catalepticus, from Greek kataleptikos, from kataleptos (see catalepsy). The noun meaning "one affected by catalepsy" is from 1851.
catalog: see catalogue.
catalogue (n.): early 15c., from Old French catalogue "list, index" (14c.), and directly from Late Latin catalogus, from Greek katalogos "a list, register, enrollment" (e.g. the katalogos neon, the "catalogue of ships" in the "Iliad"), from kata "down; completely" (see cata-) + legein "to say, count" (see lecture (n.)).
catalogue (v.): 1590s, "to make a catalogue;" see catalogue (n.). From 1630s as "to enter into a catalogue." Related: Catalogued; cataloguing.
catalpa (n.): c.1740, from an American Indian language of the Carolinas, perhaps Creek (Muskogean) /katalpa/, literally "head-wing."
catalyse (v.): variant spelling of catalyze (q.v.); for spelling, see -ize. Related: Catalysed; catalysing.
catalysis (n.): 1650s, "dissolution," from Latinized form of Greek katalysis "dissolution, a dissolving" (of governments, military units, etc.), from katalyein "to dissolve," from kata- "down" (or "completely"), see cata-, + lyein "to loosen" (see lose). Chemical sense "change caused by an agent which itself remains unchanged" is attested from 1836, introduced by Swedish chemist Jöns Jakob Berzelius (1779-1848).
catalyst (n.): "substance which speeds a chemical reaction but itself remains unchanged," 1902, formed in English (on analogy of analyst) from catalysis. Figurative use by 1943.
catalytic (adj.): 1836, from Latinized form of Greek katalytikos "able to dissolve," from katalyein (see catalysis).
catalyze (v.): 1890, back-formation from catalysis on model of analyze/analysis. Related: Catalyzed; catalyzing. Probably influenced by French catalyser (1842).
catamaran (n.): East Indies log raft, 1670s, from Tamil kattu-maram "tied wood," from kattu "tie, binding" + maram "wood, tree."
catamite (n.): "boy used in pederasty," 1590s, from Latin Catamitus, corruption of Ganymedes, the name of the beloved cup-bearer of Jupiter (see Ganymede). Cicero used it as a contemptuous insult against Antonius.
catamount (n.): 1660s, shortening of cat-o'-mountain (1610s), from cat of the mountain (early 15c.), a name aplied to various types of wildcat.
cataphract (n.): "coat of mail," Middle English, from Latin cataphractes "breastplate of iron scales," from Greek kataphraktes "coat of mail," from kataphraktos "covered up," from kataphrassein "to fortify," from kata "entirely" (see cata-) + phrassein "to fence around, enclose, defend" (cf. diaphragm).
cataplexy (n.): "the state of an animal when it is feigning death," 1883, from German kataplexie, from Greek kataplexis "stupefaction, amazement, consternation," from kataplessein "to strike down" (with fear, etc.), from kata- "down" (see cata-) + plessein "to strike, hit," from PIE *plak- (2) "to strike" (see plague (n.)). Related: Cataplectic.