Online Etymology Dictionary

Korea: by 1690s, from Chinese Gao li, name of a dynasty founded 918, literally "high serenity." Japanese Chosen is from Korean Choson, literally "land of morning calm," from cho "morning" + son "calm." Related: Korean (1610s). In early use Corea, Corean.
kos (n.): measure of distance in India (about 2 miles), from Hindi kos, from Sanskrit krosah, literally "a call, a shout;" thus, "distance within which a man's shout can be heard."
kosher (adj.): "ritually fit or pure, clean, lawful, conforming to the requirements of the Talmud" (especially of food), 1850, in early use also kasher, coshar, from Yiddish kosher, from Hebrew kasher "fit, proper, lawful," from base of kasher "was suitable, proper." Generalized sense of "correct, legitimate" is from 1896.
kowtow (n.): also kow-tow, 1804, from Chinese k'o-t'ou custom of touching the ground with the forehead while kneeling as a gesture of respect or submission, literally "knock the head," from k'o "knock, bump" + t'ou "head."
kowtow (v.): also kow-tow, 1826 in the figurative sense of "act in an obsequious manner," from kowtow (n.). Literal sense in English is from 1848. Related: Kowtowed; kowtowing.
kraal (n.): "village, pen, enclosure," 1731, South African, from colonial Dutch kraal, from Portuguese curral "pen or enclosure for animals" (see corral (n.)).
kraken (n.): sea-monster said to appear from time to time off the coast of Norway, 1755, from Norwegian dialectal krake (the -n is the definite article as a suffix), apparently a special use of krake "pole, stake, post," also "crooked tree, stunted animal or person."
The popular notion of the kraken dates back at least to the time of Pontoppidan (1698-1764), who wrote a description of it. One of the giant squids, as a cephalopod of the genus Architeuthis, might furnish a reasonable basis for the myth. [Century Dictionary]
Krakow: city in southern Poland, said to have been named for a supposed founder, Krak. Related: Krakowiak.
Kraut (n.): "a German" (especially a German soldier), 1841, but popularized during World War I, from German kraut "cabbage," considered a characteristic national dish. The "cabbage" sense is attested in English from 1855.
Krebs cycle: 1941, named for Sir Hans Adolf Krebs (1900-1981), German-born British biochemist.
Kremlin: 1660s, Cremelena, from Old Russian kremlinu, later kremlin (1796), from kreml' "citadel, fortress," a word perhaps of Tartar origin. Originally the citadel of any Russian town or city, now especially the one in Moscow (which enclosed the imperial palace, churches, etc.). Used metonymically for "government of the U.S.S.R." from 1933. The modern form of the word in English might be via French.
kreutzer (n.): small coin of Germany and Austria, 1540s, so called because formerly marked with a cross, from German Kreuz (see cross (n.)).
kriegspiel (n.): war games played on maps with blocks representing bodies of soldiers, 1873 (once, from 1811, as a German word in English), from German Kriegsspiel, literally "war game," from Krieg "war," from Middle High German kriec, "combat," mostly "exertion, effort; opposition, enmity, resistance," from Old High German chreg "stubbornness, defiance, obstinacy," perhaps from PIE *gwere- (2) "heavy" (see grave (adj.)) or cognate with Greek hybris "violence" (see hubris; also see war (n.)). For second element, see spiel (n.). Introduced 1870s as officer training in British army.
krill (n.): 1886, from Norwegian kril "small fry of fish."
kris (n.): short Malay dagger with a wavy blade, 1570s, said to be a Javanese word. In early use also spelled creese, etc.
Krishna: eighth avatar of Vishnu, 1793, from Sanskrit krshnah, literally "the Black One," from PIE *kers-no-, suffixed form of root *kers- "dark, dirty" (source also of Old Church Slavonic crunu, Russian coron, Serbo-Croatian crn, Czech cerny, Old Prussian krisnas "black," Lithuanian kersas "black and white, variegated").
Kriss Kringle: 1830, Christ-kinkle (in a Pennsylvania German context, and as a reminiscence of times past, so probably at least a generation older in that setting), from German Christkindlein, Christkind'l "Christ child." Properly Baby Jesus, not Santa Claus.
Kristallnacht (n.): in reference to the pogrom of Nov. 9-10, 1938, in Germany and Austria; from German, literally "crystal night;" often translated as "Night of Broken Glass." See crystal (n.) + night (n.).
krone (n.): currency unit and silver coin in Scandinavian countries, 1861, from Danish krone (plural kroner), Swedish krona (plural kronor), literally "crown" (see crown (n.)). Also the name of a 10-mark gold piece issued by the German Empire. So called for the devices stamped on them.
kroner (n.): see krone.
Krugerrand (n.): also Kruger rand, 1967, South African gold coin (issued for investment purposes) bearing a portrait of Transvaal President Stephanus Johannes Paulus Kruger (1825-1904); second element is rand, unit of decimal currency introduced in Republic of South Africa 1961, named for The Rand, gold-mining area in Transvaal, short for Witwatersrand (see rand).
krummhorn (n.): also crummhorn, "A medieval musical instrument of the clarinet class, having a curved tube and a melancholy sound" [Century Dictionary], 1864, from German, literally "crooked horn," from krumm "curved, crooked" (8c.), from a West Germanic *krumba- (compare Old English crumb, crump "crooked, bent, stooped," source of crumple); for second element see horn (n.).
Krupp (n.): 1883, in reference to guns made at the armaments works in Essen, Germany, founded by German metallurgist Alfred Krupp (1812-1887).
krypton (n.): inert gaseous element, 1898, coined by its discoverers (Sir William Ramsay and Morris W. Travers) from Greek krypton, neuter of adjective kryptos "hidden" (see crypt); so called because it remained undiscovered for so long and was so difficult to find. "Scientific American" (July 9, 1898) announced it as "the discovery of yet another element."
kryptonite (n.): fictional substance in the "Superman" series, where it weakens the otherwise invulnerable hero, 1943; perhaps from elements of krypton (which is a gas) + meteorite.
Ku Klux Klan: 1867, American English, originally Kuklux Klan, a made-up name, supposedly from Greek kyklos "circle" (see cycle (n.)) + English clan. Originally an organization of former Confederate officers and soldiers, it was put down by the U.S. military in the 1870s. Revived 1915 as a national racist Protestant fraternal organization, it grew to prominence but fractured in the 1930s. It had a smaller national revival 1950s as an anti-civil rights group, later with anti-government leanings. In late 19c. often simply Kuklux.
kudos (n.): "fame, renown, glory," 1799, probably originally in university slang, from Greek kydos "glory, fame," especially in battle, "a poetical word, found chiefly in the Iliad and Odyssey" [Century Dictionary], literally "that which is heard of," from PIE root *skeue- "to pay attention, perceive" (see caveat). In form the word is a Greek singular noun, but the final -s often is mistaken as a plural suffix in English, leading to the barbarous back-formation kudo (attested by 1936).
kudu (n.): South African antelope, 1777, from Kaffir (Xhosa) iqhude.
kudzu (n.): perennial climbing plant native to Japan and China, 1893, from Japanese kuzu. It was introduced in U.S. southeast as forage (1920s) and to stop soil erosion (1930s) but soon ran wild and became emblematic of anything unwanted that grows faster than it can be controlled.
kugel (n.): kind of pudding in Jewish cookery, 1846, from Yiddish kugel, literally "ball," from Middle High German kugel "ball, globe" (see cog (n.)).
kulak (n.): 1877, "relatively well-to-do Russian farmer or trader," from Russian kulak (plural kulaki) "tight-fisted person," literally "fist," from Turki (Turkish) kul "hand." In the jargon of Soviet communism, applied in contempt and derision to those who worked for their own profit.
kultur (n.): 1914, originally, "ideals of civilization as conceived by the Germans," a word from the First World War and in English always at first ironic, from German Kultur, from Latin cultura (see culture (n.)).
Kulturkampf (n.): 1879, originally in reference to the struggle (1872-86) between the German government and the Catholic Church over control of educational and ecclesiastical appointments, German, literally "struggle for culture," from Kultur + Kampf "combat, fight, struggle," from Old High German kampf (8c.), from Latin campus "field, battlefield" (see campus).
kumquat (n.): 1690s, from Chinese (Cantonese) kamkwat, from kam "golden" + kwat "orange." Said in OED to be a Cantonese dialectal form of Chinese kin-ku.
kung fu (n.): also kung-fu, 1966, from dialectal Chinese kung fu, said to meant literally "merit master," but Barnhart has it as "boxing method."
kunst (n.): from German Kunst "art," originally "knowledge, skill" (9c.), abstract noun from the root of kennen "to know," können "know how, be able" (see can (v.)). Appearing in English in various compounds from 1899, never quite nativized.
Kuomintang: 1912, Chinese nationalist party founded by Sun Yat-Sen (led after 1925 by Chiang Kai-Shek, and after 1949 ruling in Taiwan); from kuo "nation, nationalist" + min "people" + tang "party."
Kurd: one of a people of western Asia, 1610s, the people's self-designation. Their language is Indo-European. Related: Kurdish; Kurdistan.
kurgan (n.): 1889, from Russian, originally a Tatar word.
Kuwait: Persian Gulf country, named for its capital city (said to have been founded in current form 1705), which is from Arabic al-kuwayt, diminutive of kut, a word used in southern Iraq and eastern Arabia for a fortress-like house surrounded by a settlement and protected by encircling water, and said to be ultimately from Persian. Related: Kuwaiti.
kvass (n.): Russian fermented drink made from rye or barley, 1550s, from Russian kvas, said to mean literally "leaven," from Old Church Slavonic kvasu "yeast," cognate with Latin caseus "cheese" (see cheese (n.1)).
kvetch (v.): "to complain, whine," 1953 (implied in kvetching), from Yiddish kvetshn, literally "squeeze, press," from German quetsche "crusher, presser." As a noun, from 1936 as a term of abuse for a person.
Kwa: Niger-Congo language family (including Ibo and Yoruba), 1857.
kwashiorkor (n.): 1935, from a native name in Ghana for the disease.
kylix (n.): "elegant cup or vase for drinking" (usually broad and shallow, with handles), 1873 (earlier in German), from Greek kylix "cup," cognate with Latin calix, from PIE root *kal- (1) "cup" (see chalice).
kymatology (n.): science of waves, 1906, from Greek kyma (genitive kymatos) "a wave" + -ology. Related: Kymatological; kymatologist.
Kyoto: city in Japan, from kyo + to, both meaning "capital." Founded 794 as Heionkyo "Capital of Calm and Peace," it also has been known as Miyako and Saikyo. Kyoto Protocol so called because it was initially adopted Dec. 11, 1997, in the Japanese city.
kyphosis (n.): "angular curvature of the spine," 1854 (in a translation from German, where it is attested by 1783), from Greek kyphos "crooked" + -osis.
Kyrgyz: also Kirghiz, Turkic people of western Central Asia, 1650s; their name is of disputed origin.
Kyrie eleison: early 13c., a Greek liturgical formula adopted untranslated into the Latin mass, literally "lord have mercy" (Ps. cxxii:3, Matt. xv:22, xvii:15, etc.). From kyrie, vocative of kyrios "lord, master" (see church (n.)) + eleeson, aorist imperative of eleo "I have pity on, show mercy to," from eleos "pity, mercy" (see alms). Hence, the corresponding part of a musical setting of the Mass or Anglican Communion.