Online Etymology Dictionary

karoo (n.): "barren table-land in South Africa," 1789, said to be from a Hottentot word meaning "hard," or perhaps "desert."
karst (n.): name of a high, barren limestone region around Trieste; used by geologists from 1894 to refer to similar landforms. The word is the German form of Slovenian Kras, which might be related to words in Slavic meaning "red."
kart (n.): 1957, American English, short for go-kart (see go-cart).
karyo-: before vowels kary-, word-forming element used since c. 1874 in biological terms referring to cell nuclei, from Greek karyon "nut, kernel," possibly from PIE root *kar- "hard" (see hard (adj.)).
karyotype (n.): chromosomal constitution of a cell, 1929, ultimately from Russian kariotip (1922); see karyo- + type. Related: Karyotypic.
kasbah (n.): alternative spelling of casbah.
Kashmir: formerly also Cashmere, 1747, from Sanskrit Kashypamara "land of Kashyap," said to be the name of a renowned sage. As a type of carpet, from 1900. Related: Kashmiri (1832); Kashmirian.
katabatic (adj.): of winds, "blowing down a slope," 1904, from Greek katabatos "descending," from katabainein "to go down," a compound of kata- "down" (see cata-) + bainein "to go" (see come).
katakana (n.): one of the two traditional styles of writing Japanese (along with hiragana), 1727, from Japanese katakana, from kata "side" + kana "borrowed letter(s)," short for kari-na- "borrowed names." Used now largely for writing proper names and foreign words.
katana (n.): type of long, single-edged sword, 1610s, from Japanese.
katchup: spelling variant of ketchup.
Kate: fem. proper name, pet form of Katherine. In World War II it was the Allies' nickname for the standard type of torpedo bomber used by the Imperial Japanese Navy. Kate Greenaway in reference to a style of children's clothing is from 1902, from the work of the English illustrator of children's books who was very popular c. 1880.
kathenotheism (n.): "a form of polytheism characteristic of the Vedic religion, in which one god at a time is considered supreme," 1865, coined in German by Max Müller from Greek kath' hena "one by one" (from kata- "according to" + en- "one") + theism. Müller also coined the nearly synonymous henotheism (1860, from Greek henos "one") for "faith in a single god" as distinguished from exclusive belief in only one god, in writings on early Hebrew religion.
Katherine: fem. proper name, also Katharine; see Catherine.
Kathmandu: Nepalese capital, from Nepalese Kathmandu, from kath "wooden" + mandu "temple."
Katie: fem. proper name, diminutive form of Kate. Noun Katie-bar-the-door "a brouhaha, a turbulent and combative situation" is by 1888; the notion is "get ready for trouble."
katydid (n.): insect of the locust family, 1784, American English (perhaps first used by John Bartram), imitative of the stridulous sound the male makes when it vibrates its wings. In the eastern U.S., a familiar sound of a summer night; the sound itself was more accurately transcribed in 1751 as catedidist.
[T]heir noise is loud and incessant, one perpetually and regularly answering the other in notes exactly similar to the words Katy did, or Katy Katy did, repeated by one, and another immediately bawls out Katy didn't, or Katy Katy didn't. In this loud clamour they continue without ceasing until the fall of the leaf, when they totally disappear. [J.F.D. Smyth, "A Tour in the United States of America," 1784]
katzenjammer (n.): 1821, in a German context, "a hangover," American English colloquial, from German Katzenjammer "hangover" (18c.), also figuratively, in colloquial use, "remorse of conscience, vow to mend one's ways," literally "wailing of cats, misery of cats," from katzen, comb. form of katze "cat" (see cat (n.)) + jammer "distress, wailing" (see yammer (v.)).
Pleasure can intoxicate, passion can inebriate, success can make you quite as drunk as champagne. The waking from these several stages of delights will bring the same result--Katzenjammer. In English you would call it reaction; but whole pages of English cannot express the sick, empty, weary, vacant feeling which is so concisely contained within these four German syllables. ["Blackwood's Edinburgh Magazine," August 1884]
Katzenjammer Kids "spectacularly naughty children" is from the title of the popular newspaper comic strip (based on the German Max und Moritz stories) first drawn by German-born U.S. comic strip artist Rudolph Dirks (1877-1968) in 1897 for the "New York Journal." Hence, katzenjammer in the sense "any unpleasant reaction" (1897). The strip was temporarily de-Germanized during World War I:
"THE SHENANIGAN KIDS" is the new American name for the original "Katzenjammer Kids." Although the original name and idea were pure Holland Dutch, some people may have had the mistaken impression that they were of Germanic origin, and hence the change. It is the same splendid comic as in the past. [International Feature Service advertisement in "Editor & Publisher," July 6, 1918]
Kay: fem. proper name, often a shortening of Katherine. As a given name for girls, from 1890s in the U.S.; among the top 100 names for girls born there 1936-1945.
kayak (n.): type of Eskimo light boat, originally made from seal-skins stretched over a wooden frame, 1757, kajak, from Danish kajak, from Greenland Eskimo qayaq, literally "small boat of skins." The verb is attested from 1875, from the noun. Related: Kayaking; kayaker (1856).
Kayla: fem. proper name, usually an extended form of Kay. Rare before 1962; a top-20 name for girls born in the U.S. 1988-2004.
kayles (n.): old game similar to bowls except a club or stick was thrown instead of a ball, from kail, from Middle English kayle "a pin, ninepin, skittlepin;" cognate with German Kegel, Danish kegle. Also the name of a game with nine holes drilled in the ground (an iron ball is rolled among them).
kayo: spelled-out form of K.O. (for knockout in the pugilism sense), from 1923. Also used in 1920s as a slang reversal of OK.
Kazakhstan: from the indigenous Kazakh people (whose name is from Turkic kazak "nomad;" see Cossack) + Iranian -stan "country, land" (see -stan).
Kazimir: masc. proper name; see Casimir.
kazoo (n.): 1884, American English, a commercial name, probably an alteration of earlier bazoo "trumpet" (1877), which probably is ultimately imitative (compare bazooka). In England, formerly called a Timmy Talker, in France, a mirliton.
Kazoos, the great musical wonder, ... anyone can play it; imitates fowls, animals, bagpipes, etc. [1895 Montgomery Ward catalogue, p.245]
Mostly "etc."
Keatsian (adj.): 1836, "of or in the manner of English poet John Keats" (1795-1821).
kebab (n.): "pieces of meat roasted on a skewer," 1783 (compare shish kebab).
keck (v.): "to heave as if to vomit," 1530s, imitative of the sound involved. Related: Kecked; kecking; keckish.
Ked: proprietary name of a brand of canvas sneakers, 1917, registered by United States Rubber Co., N.Y. Based on Latin ped-, stem of pes "foot" (see foot (n.))
"We wanted to call it Peds, but ... it came too close to ... other brand names. So we batted it around for awhile and decided on the hardest-sounding letter in the alphabet, K, and called it Keds, that was in 1916." [J.Healey, in R.L. Cohen, "Footwear Industry," x.93]
kedge (v.): "to move (a ship) by means of a light cable attached to an anchor," 1620s, probably from a Scandinavian source or perhaps from cadge (v.) "to tie, fasten" (itself from Scandinavian); compare colloquial ketch from catch. Hence also kedge-anchor (1704) and its shortened form kedge (1769).
keel (n.): "lowest and principal timber of a ship or boat," mid-14c., probably from a Scandinavian source (compare Old Norse kjölr "keel," Danish kjøl, Swedish köl), which according to Watkins is from Proto-Germanic *gwele- (3) "to swallow" (see gullet).

OED and Middle English Dictionary says this word is separate from the keel that means "a strong, clumsy boat, barge" (c. 1200), which might be instead from Middle Dutch kiel "ship" (cognate with Old English ceol "ship's prow," Old High German kiel, German Kiel "ship"). But the two words have influenced each other or partly merged, and Barnhart calls them cognates. Keel still is used locally for "flat-bottomed boat" in the U.S. and England, especially on the Tyne.

In historical writing about the Anglo-Saxons, it is attested from 17c. as the word for an early form of long-boat supposedly used by them in the crossing, based on ceolum in the Anglo-Saxon Chronicle and Medieval Latin cyulis (Gildas). Old English also used simply scipes botm or bytme. On an even keel (1560s) is "in a level, horizontal position," hence figurative extension with reference to stability.
keel (v.1): of a ship, "turn keel-up" (intransitive), 1828, from keel (n.). To keel over is to "capsize" (1829), hence generally "tumble, fall" (1833), from the nautical image of a ship turning keel-up, an extended sense first in sporting, in reference to shot game. Related: Keeled; keeling.
keel (v.2): "to keep cool, make cool," Middle English kelen, from Old English celan "to cool," from Proto-Germanic *koljan "to cool," from the same source as cool (adj.). The form kele (from Old English colian) was used by Shakespeare, but later it was assimilated with the adjective form into the modern verb cool. Cognate with Dutch koelen, Old High German chuolen, German kühlen.
keelboat (n.): 1690s, from keel (n.) + boat (n.).
keeled (adj.): "furnished with a keel, having a keel (of a specified type) or something resembling one," 1744, adjective from keel (n.).
keelhaul (v.): 1660s (the experience itself is described from 1620s), from Dutch kielhalen, literally "to haul under the keel," an old punishment for certain offenses; from kiel- (see keel (n.)) + halen "to haul, pull" (see haul (v.)). Related: Keelhauled. German kielholen, Danish kjølhale, Swedish kölhala also are from Dutch. Related: Keelhauling.
keelson (n.): also kelson, 1620s, altered (by influence of keel (n.)) from Middle English kelsyng (late 13c.), which probably is of Scandinavian origin (compare Swedish kölsvin, Danish and Norwegian kjølsvin), from a compound of words such as Old Norse kjölr (see keel (n.)) + swin "swine," which was used of timber (see swine). Or else from a similarly formed Low German source.
keen (adj.): c. 1200, from Old English cene "bold, brave, fearless," in later Old English "clever, prudent, wise, intelligent," common Germanic (cognate with Old Norse kænn "skillful, wise," Middle Dutch coene "bold," Dutch koen, Old High German kuon "pugnacious, strong," German kühn "bold, daring"), but according to OED there are no cognates outside Germanic and the original meaning is "somewhat obscure"; it seem to have been both "brave" and "skilled." Perhaps the connection notion was "to be able" and the word is connected to the source of can (v.1).

Sense of "eager (to do something), vehement, ardent" is from c. 1300. The physical meaning "sharp, sharp-pointed, sharp-edged" (c. 1200) is peculiar to English. Extended senses from c. 1300: Of sounds, "loud, shrill;" of cold, fire, wind, etc. "biting, bitter, cutting." Of eyesight c. 1720. A popular word of approval in teenager and student slang from c. 1900. Keener was 19c. U.S. Western slang for a person considered sharp or shrewd in bargaining.
keen (v.): "lament loudly over the dead, bitterly wail," 1811, from Irish caoinim "I weep, wail, lament," from Old Irish coinim "I wail." Hence "to utter in a shrill voice" (1893). Related: Keened; keener; keening. As a noun from 1830.
keenly (adv.): Old English cenlice "boldly;" see keen (adj.) + -ly (2). Meaning "incisively, with intensity, acutely" is from c. 1200; that of "cuttingly" is from 1590s.
keenness (n.): 1520s, from keen (adj.) + -ness.
keep (v.): late Old English cepan (past tense cepte) "to seize, hold; seek after, desire," also "to observe or carry out in practice; look out for, regard, pay attention to," from Proto-Germanic *kopjan, which is of uncertain origin.

Old English cepan was used c. 1000 to render Latin observare, so perhaps it is related to Old English capian "to look" (from Proto-Germanic *kap-), which would make the basic sense "to keep an eye on, see to it."
The word prob. belonged primarily to the vulgar and non-literary stratum of the language; but it comes up suddenly into literary use c. 1000, and that in many senses, indicating considerable previous development. [OED]
The senses exploded in Middle English: "to guard, defend" (12c.); "restrain (someone) from doing something" (early 13c.); "take care of, look after; protect or preserve (someone or something) from harm, damage, etc." (mid-13c.); "preserve, maintain, carry on" a shop, store, etc. (mid-14c.); "prevent from entering or leaving, force to remain or stay" (late 14c.); "preserve (something) without loss or change," also "not divulge" a secret, private information, etc., also "to last without spoiling" (late 14c.); "continue on" (a course, road, etc.), "adhere to" a course of action (late 14c.); "stay or remain" (early 15c.); "to continue" (doing something) (mid-15c.). It is used to translate both Latin conservare "preserve, keep safe" and tenere "to keep, retain."

From 1540s as "maintain for ready use;" 1706 as "have habitually in stock for sale." Meaning "financially support and privately control" (usually in reference to mistresses) is from 1540s; meaning "maintain in proper order" (of books, accounts) is from 1550s.

To keep at "work persistently" is from 1825; to keep on "continue, persist" is from 1580s. To keep up is from 1630s as "continue alongside, proceed in pace with," 1660s as "maintain in good order or condition, retain, preserve," 1680s as "support, hold in an existing state." To keep it up "continue (something) vigorously" is from 1752. To keep to "restrict (oneself) to" is from 1711. To keep off (trans.) "hinder from approach or attack" is from 1540s; to keep out (trans.) "prevent from entering" is from early 15c.
keep (n.): mid-13c., "care or heed in watching," from keep (v.). Meaning "innermost stronghold or central tower of a castle" is from 1580s; OED says this is perhaps a translation of Italian tenazza, the notion being "that which keeps" (someone or something). The sense of "food required to keep a person or animal" is attested from 1801 (to earn (one's) keep is from 1885). For keeps "completely, for good" is American English colloquial, from 1861, probably from the notion of keeping one's winnings in games such as marbles.
keep-away (n.): as a game, 1925, from verbal phrase (attested from late 14c.); see keep (v.) + away (adv.).
keepable (adj.): 1839, from keep (v.) + -able.
keeper (n.): c. 1300 (late 13c. as a surname), "one who has charge of some person or thing, warden," agent noun from keep (v.). Sense of "one who carries on some business" is from mid-15c. Sporting sense (originally cricket) is from 1744. Meaning "something (or someone) worth keeping" is attested by 1999. Brother's keeper is from Genesis iv:9.
keeping (n.): "care, custody, charge," c. 1300, verbal noun from keep (v.). Phrase in keeping with "in harmony or agreement with" (1806) is from use of keeping in the jargon of painting to refer to a pleasing harmony of the elements of a picture (1715).
keepsake (n.): 1790, from keep (v.) + sake; an unusual formation on model of namesake; thus an object kept for the sake of the giver. Used early 19c. in titles of holiday gift books. As an adjective by 1839.
kef (n.): "state of dreaming intoxication produced by smoking cannabis," 1808, from Arabic kaif "well-being, good-humor; dolce far niente." In Morocco and Algeria, it was said to be the name for Indian hemp.