Online Etymology Dictionary

keg (n.): 1630s, earlier kag (mid-15c.), from a Scandinavian source such as Old Norse kaggi "keg, cask," of unknown origin. Cognate with Swedish kagge, Norwegian kagg. Specific sense of "small or half barrel of beer" is from 1945. U.S. student slang kegger "party featuring a keg of beer" attested by 1969.
keister (n.): "buttocks," 1931, perhaps transferred from the same word in an underworld meaning "safe, strongbox" (1914), earlier "a burglar's toolkit that can be locked" (1881); probably from British dialect kist (northern form of chest (n.)) or its German cognate Kiste "chest, box." The connection of the word to the body part might be via the pickpocket slang sense of "rear trouser pocket" (1930s).
keld (n.): "a spring," 1690s, limited to northern dialect, but frequent in place names; from Old Norse kelda "a well, fountain, spring," also "a deep, still, smooth part of a river," from a Germanic verbal root represented by German quellen "to swell, spring, gush."
Kellogg: surname, attested from late 13c. (Gilbert Kelehog), literally "kill hog," a name for a butcher (compare kill-buck, a medieval surname, also noted as a term of contempt for a butcher). The U.S. cereal company began in Battle Creek, Michigan, in 1906, founded by W.K. Kellogg (1860-1951), business manager of the Battle Creek Sanatorium, as Battle Creek Toasted Corn Flake Company.
Kelly: common Irish surname, from Old Irish ceallach "war." As a type of pool played with 15 balls, it is attested from 1898. Kelly green first recorded 1917.
keloid (n.): also cheloid, 1854, from French kéloïde, from Greek khele "crab claw, talon, cloven hoof" + -oides (see -oid). Related: Keloidal; cheloidal.
kelp (n.): 1660s, "large seaweed," from Middle English culpe (late 14c.), a word of unknown origin. Specifically of a type of Pacific seaweed of the Americas from 1834. Kelper "native or inhabitant of the Falkland Islands" is attested from 1896.
kelpie (n.): 1747, Scottish, of unknown origin, perhaps related to Gaelic colpach "heifer, steer, colt;" colpa "cow, horse." The Lowland name of a demon in the shape of a horse that was reputed to haunt lakes and rivers and to delight in causing drownings. But unlike its equivalents in Danish (nøkken) and Icelandic (nykur), it occasionally was benevolent, especially to millers by keeping their streams running.
Kelvin: unit of absolute temperature scale, 1911, in honor of British physicist Sir William Thompson, Lord Kelvin (1824-1907).
kempt (adj.): "well-combed, neat," late 14c., from past tense of archaic kemb "to comb," from Old English cemdan (see unkempt). A rare word after c. 1500; any modern use probably is a whimsical back-formation from unkempt.
ken (v.): "to know, understand, take cognizance of," a word surviving mainly in Scottish and northern England dialect, from Middle English kennen, "make known; give instruction to; be aware, know, have knowledge of, know how to; recognize by sight; see, catch sight of," a very common verb, from Old English cennan "make known, declare, acknowledge" (in late Old English also "to know"), originally "cause to know, make to know," causative of cunnan "to become acquainted with, to know" (see can (v.)). Cognate with German kennen, Danish kjende, Swedish känna. Related: Kenned; kenning.
ken (n.2): "house used as a meeting place by thieves or other disreputable characters," 1560s, vagabonds' slang, probably a shortening of kennel (n.).
ken (n.1): 1550s, "cognizance, intellectual view;" 1580s in a physical sense, "range of sight;" from ken (v.), in the second sense perhaps via kenning (n.2) in the same sense in nautical use.
kendal (n.): green woolen cloth, late 14c., from place name in Westmoreland where it was manufactured. The place (which is in the Domesday Book) is "Kent-dale," so called for being in the dale of the River Kent.
Kenelm: masc. proper name, Old English Cenhelm, from cene "brave, bold" (see keen (adj.)) + helm "helmet" (see helmet (n.)).
Kennedy: Irish surname, said to be from Old Irish cinneide "ugly head."
kennel (n.): c. 1300, from Anglo-French *kenil, French chenil (attested from 16c. but probably older), from Vulgar Latin *canile, from Latin canis "dog" (see canine (n.)). With suffix denoting a place where animals are kept, as in ovile "sheepfold" from ovus, equile "horse-stable" from equus, etc. Kennel club is attested from 1857.
kennel (v.): 1550s (intransitive) "live in a kennel;" 1590s (transitive) "house in or as in a kennel;" from kennel (n.). Related: Kenneled; kenneling.
Kenneth: masc. proper name, Scottish, from Gaelic Caioneach, literally "handsome, comely."
kenning (n.1): "periphrastic expression in early Germanic poetry" (such as swan-road for "sea," sky-candle for "sun"), 1871, a modern learned word from Old Norse kenning in a special sense "poetical periphrasis or descriptive name" (it also meant "teaching, doctrine; preaching; mark of recognition"), from kenna "to know, to recognize, to feel or perceive; to call, to name (in a formal poetic metaphor)."
In the whole poem of Beowulf there are scarcely half a dozen of them [similes], and these of the simplest character, such as comparing a ship to a bird. Indeed, such a simple comparison as this is almost equivalent to the more usual "kenning" (as it is called in Icelandic), such as "brimfugol," where, instead of comparing the ship to a bird, the poet simply calls it a sea-bird, preferring the direct assertion to the indirect comparison. [Henry Sweet, "Sketches of the History of Anglo-Saxon Poetry," London, 1871]
Cognate Old English cenning is attested as "procreation; declaration in court" (and see kenning (n.2)).
kenning (n.2): early 14c., "sign, token; teaching, instruction;" c. 1400, "range of vision," also "mental cognition;" late 15c., "sight, view;" verbal nouns from ken (v.).
keno (n.): game of chance (akin to bingo), 1814, American English, probably from French quine "five winning numbers in a lottery," from Latin quini "five each," distributive of quinque "five" (see five). The numbers are arranged in rows of five.
keno-: before vowels, ken-, word-forming element meaning "empty," from Greek kenos "empty," from PIE root *ken- (3) "empty."
kenosis (n.): "self-limitation of God at the Annunciation," 1873, from Greek kenosis "an emptying," from kenoein "to empty," from PIE *ken- (3) "empty." From Phil. ii:7. Related: Kenotic.
kenspeck (adj.): "known by marks, conspicuous, easily recognizable," 1580s, from Old Norse kennispeki "the faculty of recognition," from kenni "a mark" + speki "wisdom," from spakr "wise." Sometimes kenspeckled (1714), as though "conspicuous because marked with speckles or freckles."
Kent: southeasternmost county of England, Old English Cent, Cent lond, Centrice, from Latin Cantia, Canticum (Caesar), Greek Kantion (Strabo, 51 B.C.E.), from an ancient British Celtic name often explained as "coastal district," or "corner-land, land on the edge," but possibly "land of the hosts or armies." Related: Kentish (Old English Centisc).
Kentucky: U.S. state (admitted 1792), earlier a county of Virginia (organized 1776); the name is of Iroquois or Shawnee origin, perhaps a Wyandot (Iroquoian) word meaning "meadow" (compare Seneca geda'geh "at the field"); the original use in English seems to have been the river name; the native use perhaps was first in reference to a village in what now is Clark County known in Shawnee as Eskippakithiki. Related: Kentuckian.
Kenya: African nation, named for Mount Kenya, which probably is a shortening of Kikuyu Kirinyaga, from kere nyaga, literally "white mountain" (though just south of the equator, it is snowcapped). Related: Kenyan.
kepi (n.): soldier's peaked cap, 1861, from French képi (19c.), from German Swiss käppi, diminutive of German Kappe "a cap," from Late Latin cappa "hood, cap" (see cap (n.)). The usual style of uniform cap in the American Civil War.
kept (adj.): 1670s, past participle adjective from keep (v.).
ker-: U.S. slang prefix, by 1836 as che-, 1843 as ker-, possibly from influence of German or Dutch ge-, past participial prefixes; or ultimately echoic of the sound of the fall of some heavy body.
keratin (n.): basic substance of horns, nails, feathers, etc., 1848, from Greek keras (genitive keratos) "horn of an animal; horn as a substance" (from PIE *ker- (1) "horn, head;" see horn (n.)) + chemical suffix -in (2).
kerato-: before vowels, kerat-, scientific word-forming element meaning "horn, horny," also "cornea of the eye" (see cornea), from Greek keras (genitive keratos) "the horn of an animal; horn as a material," from PIE *ker- (1) "horn, head" (see horn (n.)).
kerb (n.): 1660s, a spelling variant of curb (n.); in early use also kirb. It is the preferred British English spelling in certain specialized senses, especially "edging of stone on a pavement" (1805). Related: Kerbing; kerbstone.
kerchief (n.): "square piece of fabric folded and worn about the head," early 13c., kovrechief "piece of cloth used to cover part of the head," especially a woman's head-cloth or veil, from Anglo-French courchief, Old French couvrechief "a kerchief," literally "cover head," from couvrir "to cover" (see cover (v.)) + chief "head" (see chief). From late 14c. as "piece of cloth used about the person" generally, for purposes other than covering the head; and from c. 1400 as "piece of cloth carried in the hand" to wipe the face, etc. (compare handkerchief).
kerfuffle (n.): "row, disturbance," 1970; from 1946 as kafuffle, said to have been used c. 1930 in Canadian English, ultimately from Scottish curfuffle.
kermes (n.): c. 1600, "shield louse (Coccus ilicis) that yields a red dye" (1590s of the tree on which the insects live), from Medieval Latin cremesinus (also source of French kermès, Italian chermes, Spanish carmes), from Arabic qirmiz "kermes," from Sanskrit krmi-ja a compound meaning "(red dye) produced by a worm."

The Sanskrit compound is krmih "worm" (from PIE root *kwrmi- "worm," source also of Lithuanian kirmis, Old Irish cruim, Albanian krimp "worm") + -ja- "produced" (from PIE *gene-; see genus). The insect lives in the Levant and southern Europe on a species of small evergreen oak (kermes oak) and in ancient Europe were the main source of red and scarlet dye. The dye is prepared from the dried bodies of pregnant females, which alive resemble small roundish grains about the size of peas and cling immobile to the tree on which they live. From this fact kermes dye was, for a long time, mistaken as being from a seed or excrescence of the tree, and the word for it in Greek was kokkos, literally "a grain, seed" (see cocco-). This was passed to Latin as coccum, coccus "berry [sic] yielding scarlet dye," in late use "scarlet color, scarlet garment."

So important was kermes (coccus) as a commercial source of scarlet dye that derivatives of the name for it have displaced the original word for "red" in many languages, such as Welsh coch (from Latin), Modern Greek kokkinos. Also compare Russian čcermnyj "purple-red," Old Church Slavonic čruminu. Compare also crimson (n.).

Kermes dyes have been found in burial wrappings in Anglo-Scandinavian York, but the use of kermes dyes seems to have been lost in Europe from the Dark Ages until early 15c. It fell out of use again with the introduction of cochineal (the word for which itself might be from coccus) from the New World.
Cloths dyed with kermes are of a deep red colour; and though much inferior in brilliancy to the scarlet cloths dyed with real Mexican cochineal, they retain the colour better and are less liable to stain. The tapestries of Brussels and other parts of Flanders, which have scarcely lost any thing of their original brilliancy, even after a lapse of 200 years, were all dyed with kermes. [W.T. Brande, "Dictionary of Science, Literature, & Art," London, 1842]
kern (n.): 1680s, "part of a metal type projecting beyond the body," as the head of an -f- or the tail of a -j-. According to Century Dictionary this is identical with kern "a grain" (see kernel), but OED says it is from French carne "projecting angle, quill of a pen" (12c.), Old North French form of Old French charne "hinge, pivot," from Latin cardinem "hinge." Related: Kerned "having the top or bottom projecting beyond the body;" kerning.
kernel (n.): "edible substance in a nut or the stone of a fruit," Old English cyrnel "seed, kernel, pip," from Proto-Germanic *kurnilo- (source also of Middle High German kornel "a grain," Middle Dutch cornel "coarse meal"), from the root of corn "seed, grain" (see corn (n.1)) + -el, diminutive suffix. Figurative sense of "core or central part of anything" is from 1550s.
kerosene (n.): "mixture of liquid hydrocarbons used as an illuminating or heating fluid," 1852, from Greek keros "wax" (see cere) + chemical suffix -ene. Coined irregularly by Canadian geologist Abraham Gesner (1797-1864), who discovered how to distill it c. 1846. So called because it contains paraffin (hence the British English name, paraffin oil).
kersey (n.): type of coarse woolen cloth, common 14c.-16c., late 14c., said to be from the name of the village in Suffolk, which supposedly is connected with the original manufacture of the cloth.
kerygma (n.): "preaching," 1879, from Greek kerygma "proclamation, that which is cried by a herald, public notice," used in the Greek New Testament for "preaching," from keryssein "to proclaim, to cry (as a herald)," from or related to keryx "herald, messenger," a word of uncertain origin, perhaps from PIE root *kar- (2) "to praise loudly," but Beekes says probably pre-Greek. Related: Kerygmatic.
kestrel (n.): kind of small falcon, windhover, c. 1600, earlier castrell (15c.), probably from Old French cresserele (13c.), earlier cercelle (Modern French crécelle), a word of obscure origin. Perhaps it is related to French crecerelle "rattle," from Latin crepitacillium "small rattle," diminutive of crepitaculum "noisy bell, rattle," from crepitare "to crackle, rattle;" possibly from the old belief that their noise frightened away other hawks. The intrusive -t- probably developed in French.
ketamine (n.): 1966, from keto- (before vowels ket-), comb. form of ketone, + amine.
ketch (n.): kind of small, strong, two-masted sailing vessel, 1650s, earlier catch (mid-15c.), cache (late 14c.), probably from Middle English cacchen "to capture, ensnare, chase" (see catch (v.)). Compare the sense development in yacht.
ketchup (n.): 1711, said to be from Malay kichap, but probably not original to Malay. It might have come from Chinese koechiap "brine of fish," which, if authentic, perhaps is from the Chinese community in northern Vietnam [Terrien de Lacouperie, in "Babylonian and Oriental Record," 1889, 1890]. Catsup (earlier catchup, 1680s) is a failed attempt at Englishing, still in use in U.S., influenced by cat and sup.

Originally a fish sauce made from various plant juices, the word came to be used in English for a wide variety of spiced gravies and sauces; "Apicius Redivivus; or, the Cook's Oracle," by William Kitchiner, London, 1817, devotes 7 pages to recipes for different types of catsup (his book has 1 spelling of ketchup, 72 of catsup), including walnut, mushroom, oyster, cockle and mussel, tomata, white (vinegar and anchovies figure in it), cucumber, and pudding catsup. Chambers's Encyclopaedia (1870) lists mushroom, walnut, and tomato ketchup as "the three most esteemed kinds." Tomato ketchup emerged c. 1800 in U.S. and predominated from early 20c.
ketone (n.): chemical group, 1851, from German keton (1848), coined by German chemist Leopold Gmelin (1788-1853) from German Aketon, from French acétone (see acetone). "Appar. an arbitrary variation of acetone, to make a distinction" [Century Dictionary]. Its combining form is keto-. Related: Ketonic.
ketosis (n.): 1900, from keto-, comb. form of ketone, + -osis.
kettle (n.): "metal vessel used for boiling or heating liquids over a flame," Old English cetil, citel (Mercian), from Proto-Germanic *katilaz (compare Old Saxon ketel, Old Frisian zetel, Middle Dutch ketel, Old High German kezzil, German Kessel), which usually is said to be derived from Latin catillus "deep pan or dish for cooking," diminutive of catinus "deep vessel, bowl, dish, pot," from Proto-Italic *katino-.
This word has been connected with Greek forms such as [kotyle] "bowl, dish." Yet the Greek word is no perfect formal match, and words for types of vessels are very often loanwords. It seems best to assume this for catinus too. [de Vaan]
One of the few Latin loan-words in Proto-Germanic, along with *punda- "measure of weight or money" (see pound (n.1)) and a word relating to "merchant" that yielded cheap (adj.). "[I]t is striking that all have something to do with trade" [Don Ringe, "From Proto-Indo-European to Proto-Germanic," Oxford 2006]. Perhaps the Latin word was confused with a native Germanic one. Spelling with a -k- (c. 1300) probably is from influence of Old Norse cognate ketill. The smaller sense of "tea-kettle" is attested by 1769.

Kettle of fish "complicated and bungled affair" (1715), sometimes is said to be from a Scottish custom of a kettle full of fish cooked al fresco at a boating party or picnic, but this custom is not attested by that phrase until 1790. Perhaps it is rather a variant of kittle/kiddle "weir or fence with nets set in rivers or along seacoasts for catching fish" (c. 1200, in the Magna Charta as Anglo-Latin kidellus), from Old French quidel, probably from Breton kidel "a net at the mouth of a stream." Kettle was used in geology for "deep circular hollow in a river bed or other eroded area, pothole" (1866), hence kettle moraine (1883), characterized by such features.
kettledrum (n.): 1540s, from kettle + drum (n.). So called for its shape. Related: Kettledrummer.