Online Etymology Dictionary

Jeff (n.): shortened or familiar form of masc. proper name Jeffrey; in early to mid-20c., sometimes used by African-Americans to indicate a Southern rural poor white person, probably from Jeff Davis, president of the Confederate States of America.
Jeffersonian: 1799 (n.), 1800 (adj.), in reference to the politics and policies of U.S. politician and statesman Thomas Jefferson, first great leader of the Democratic Party and president 1801-09. The surname, literally "son of Geoffrey," is attested from mid-14c.; in Middle English also Jeffrison, Geffreysone, Geffrason. Jeffersonianism is from 1804 in reference to the political beliefs of Thomas Jefferson; often it means advocacy of the greatest possible individual and local freedom and corresponding restriction of the national government.
Jeffrey: masc. proper name, from Old French Jeufroi, Jefroi, variants of Geuffroi (see Geoffrey).
Jehosaphat: biblical name (II Sam. viii:16), used as a mild expletive in American English from 1857; presumably another euphemistic substitution for Jesus.
Jehovah: 1530, Tyndale's transliteration of Hebrew Tetragrammaton YHWH using vowel points of Adhonai "my lord" (see Yahweh). Used for YHWH (the full name being too sacred for utterance) in four places in the Old Testament in the KJV where the usual translation the lord would have been inconvenient; taken as the principal and personal name of God.

The vowel substitution was originally made by the Masoretes as a direction to substitute Adhonai for "the ineffable name." European students of Hebrew took this literally, which yielded Latin JeHoVa (first attested in writings of Galatinus, confessor to Leo X, 1516). Jehovah's Witnesses "member of Watchtower Bible and Tract Society" first attested 1933; the organization founded c. 1879 by Charles Taze Russell (1852-1916); the name from Isa. xliii:10.
Jehovist (n.): 1844 as the name given by scholars to the presumed author or authors of the parts of the Hexateuch in which the divine name is written Yhwh (see Jehovah) + -ist. Opposed to the Elohist. Sometimes Jahvist is used. Related: Jehovistic.
Jehu: "fast, skillful driver," 1680s, from Jehu, a king of Israel in the Old Testament, who "driveth furiously" (II Kings ix:20). Sometimes also a generic name for "a coachman."
jejune (adj.): 1610s, "dull in the mind, flat, insipid, wanting in interest," from Latin ieiunus "empty, dry, barren," literally "fasting, hungry," a word of obscure origin. Related: jejunal; jejunally.
jejunum (n.): second division of the small intestine, late 14c., from Modern Latin noun use of Latin ieiunum, neuter of ieiunus "empty" (see jejune). Translating Greek nestis (Galen). So called because it typically is found empty during dissections, perhaps because it would tend to drain in a body laid on its back.
Jekyll and Hyde: in reference to opposite aspects of a person's character is a reference to Robert Louis Stevenson's story, "The Strange Case of Dr. Jekyll and Mr. Hyde," published in 1886. Jekyll, the surname of the respectful and benevolent man, is of Breton origin and was originally a personal name. Hyde in reference to the dark, opposite side of one's personality is from 1887.
"Though so profound a double-dealer, I was in no sense a hypocrite. Both sides of me were in dead earnest; I was no more myself when I laid aside restraint and plunged in shame, than when I labored, in the eye of day, at the furtherance of knowledge or the relief of sorrow and suffering." [Robert Louis Stevenson, "The Strange Case of Dr. Jekyll and Mr. Hyde," 1886]
jell (v.): "assume the consistence of jelly," 1869, American English, probably a back-formation of jelly (n.). Related: Jelled; jelling. Figurative sense is first attested 1908. Middle English had gelen "congeal," but it disappeared after 15c.
Jell-O (n.): also sometimes Jello, trademark for powdered gelatin food, advertised from 1900 by Genesee Pure Food Co., Le Roy, N.Y.
jellied (adj.): 1590s, "of the consistency of jelly;" 1895, sweetened with jelly; past participle adjective from jelly (v.).
jelly (n.): late 14c., gelee, gelle, gelly, "semisolid substance from animal or vegetable material, spiced and used in cooking; chopped meat or fish served in such a jelly," from Old French gelee "a jelly," also "a frost," noun use of fem. past participle of geler "to congeal, to freeze," from Latin gelare "to freeze, congeal, stiffen," related to gelu "frost," from PIE *gela-, suffixed form of *gel- (2) "cold; to freeze" (see cold (adj.)).

By early 15c. it was used of any jellied or coagulated substance; from 16c. as "thickened juice of a fruit prepared as food."
jelly (v.): c. 1600, transitive and intransitive, from jelly (n.). Related: Jellied; jellying.
jellybean (n.): 1905, from jelly (n.) + bean (n.). So called for its shape. Soon used in U.S. slang for "stupid person," probably encouraged by the slang sense of bean as "head."
jellyfish (n.): also jelly-fish, popular name of the medusa and similar sea-creatures, 1796, from jelly (n.) + fish (n.). So called for its soft structure. Figuratively, "person of weak character," 1883. Earlier it had been used of a type of actual fish (1707).
jellyroll (n.): also jelly-roll, "cylindrical cake containing jelly or jam," 1873, from jelly (n.) + roll (n.). As slang for "vagina; sexual intercourse" it dates from 1914 ("St. Louis Blues").
Jemima: fem. personal name, biblical daughter of Job, from Hebrew Yemimah, literally "dove" (compare Arabic yamama). The Aunt Jemima ready-mix food product in U.S. was advertised from c. 1918; the name (and image) was on baking powder advertisements by 1896. It is the title of a minstrel song credited to Joe Lang, but this is not mentioned before 1901. Previously Aunt Jemima was a name in various works of fiction and poetry, without racial aspect.
Jemmy: a popular pet form of the masc. proper name James (in Middle English records, Gemme, Jemme are more common than Jimme). In mid-18c. often associated with effeminacy and male fastidiousness; hence jemmy (adj.) "spruce, neat" (1750), jemminess (1756). As "a short crowbar," favored by burglars, from 1811. Compare jimmy (n.).
Jena: city of Thuringia, Germany, site of a famous university that dates to 16c.; attested from 9c. as Jani, from Old High German jani "strip of mown grass," ultimately from PIE root *ei- "to go" (see ion).
jennet (n.): "small Spanish horse," mid-15c., genet, from Old French genet, ginet, from Spanish jinete "a light horseman," which is probably from Arabic Zenata, name of a Barbary tribe [Klein, Dozy]. Sense transferred in English and French from the rider to the horse.
Jennifer: fem. proper name, from Welsh Gwenhwyvar, from gwen "fair, white" + (g)wyf "smooth, yielding." The most popular name for girls born in America 1970-1984; all but unknown there before 1938. Also attested as a surname from late 13c.
Jenny: fem. personal name, originally another form of Jane, Janey and a diminutive of Jane or Janet; in modern use (mid-20c.) typically a shortening of Jennifer. Jenny is attested from c. 1600 as female equivalent of jack (n.), and like it applied to animals (especially of birds, of a heron, a jay, but especially Jenny wren, 1640s, in bird-fables the consort of Robin Redbreast). Also like jack used of machinery; Akrwright's spinning jenny (1783) is said to have been named for his wife, but is perhaps rather a corruption of gin (n.2) "engine."
jeopardise (v.): chiefly British English spelling of jeopardize; for suffix, see -ize. Related: Jeopardised; jeopardising.
jeopardize (v.): 1640s, from jeopardy + -ize. Related: Jeopardized; jeopardizing. As a verb, Middle English used simple jeopard (late 14c.), a back-formation from jeopardy.
jeopardy (n.): late 14c., jupartie , ioparde, etc., "danger, risk;" earlier "a cunning plan, a stratagem" (c. 1300), from or based on Old French jeu parti "a lost game," more correctly "a divided game, game with even chances" (hence "uncertainty"). The sense perhaps developed in Anglo-French.

This is from jeu "a game" (from Latin iocus "jest;" see joke (n.)) + parti, past participle of partir "to divide" (see part (v.)). Jeopardous "in peril" (mid-15c.) is now obsolete.
Jephthah: biblical judge of Israel, from Greek Iephthae, from Hebrew Yiphtah, literally "God opens," imperfective of pathah "he opened" (compare pethah "opening, entrance").
jerboa (n.): small desert rodent, 1660s, Modern Latin, from Arabic jarbu "flesh of the loins," also the name of a small jumping rodent of North Africa. So called for the strong muscles of its hind legs. Compare gerbil.
jeremiad (n.): a complaining tirade in a tone of grief or distress, 1780, from French jérémiade (1762), in reference to "Lamentations of Jeremiah" in the Old Testament.
Jeremiah: masc. proper name, Old Testament prophet (compare jeremiad) who flourished c. 626-586 B.C.E., from Late Latin Jeremias, from Hebrew Yirmeyah, probably literally "may Jehovah exalt," but Klein suggests it also might be short for Yirmeyahu "the Lord casts, the Lord founds," and compares the first element in Jerusalem. The vernacular form in English was Jeremy.
Jeremy: popular Englished form of Jeremiah (q.v.); compare French Jérémie.
Jericho: Biblical city (Num. xxii:1, etc.), perhaps ultimately from Hebrew yareakh "moon, month," and thus a reference to an ancient moon cult. As a figurative place of retirement (17c.), the reference is to II Sam. x:5.
jerk (v.1): "to pull with sudden energy," 1580s; earlier "to lash, strike as with a whip" (1540s, surviving only in dialect), of uncertain origin, perhaps echoic. Intransitive sense of "make a sudden spasmodic motion" is from c. 1600. A soda jerk attested from 1883, from the pulling motion required to work the taps. Soda jerk (1915) is so called for the pulling motion required to work the taps.

Compare Middle English yerkid, an adjective apparently meaning "pulled tight" (early 15c.), which has the form of a past participle. Also compare Middle English ferken "move hastily; drive (something) forward," from Old English fercian "to proceed." Related: Jerked; jerking.
jerk (n.2): "tedious and ineffectual person," 1935, American English carnival slang, of uncertain origin. Perhaps from jerkwater "petty, inferior, insignificant" [Barnhart, OED]; alternatively from, or influenced by, verbal phrase jerk off "masturbate" [Rawson]. The lyric in "Big Rock Candy Mountain," sometimes offered as evidence of earlier use, apparently is "Where they hung the Turk [not jerk] that invented work."
jerk (n.1): 1550s, "stroke of a whip," from jerk (v.1). Sense of "sudden sharp pull or twist" first recorded 1570s. Meaning "involuntary spasmodic movement of limbs or features" first recorded 1805. As the name of a popular dance, it is attested from 1966.
jerk (v.2): "preserve (meat) by cutting into long thin strips and drying in the sun," 1707, American English, from American Spanish carquear, from charqui (see jerky). Related: Jerked.
jerk off (v.): slang, "perform male masturbation," by 1896, from jerk (v.) denoting rapid pulling motion + off (adv.). Compare come off "experience orgasm" (17c.). Farmer & Henley also list as synonyms jerk (one's) jelly and jerk (one's) juice. The noun jerk off or jerkoff as an emphatic form of jerk (n.2) is attested by 1968. As an adjective from 1957.
jerkin (n.): "short, close-fitting men's jacket" popular 16c.-17c., 1510s, of uncertain origin, perhaps related to Dutch jurk "a frock," but this is a modern word, itself of unknown origin, and the initial consonant presents difficulties (Dutch -j- typically becomes English -y-).
jerkwater (adj.): also jerk-water, "petty, inferior, insignificant," 1890, earlier in reference to certain railroad trains and lines (1878); in both cases the notion is of a steam locomotive crew having to take on boiler water from a trough or a creek because there was no water tank; see jerk (v.1) + water (n.1). This led to an adjectival use of jerk as "inferior, insignificant;" hence also jerkwater town (1893).
jerky (n.): 1850, American English, from American Spanish charqui "jerked meat," from Quechua (Inca) ch'arki "dried flesh."
jerky (adj.): "characterized by jerks, spasmodic," 1819, originally in medical writing with reference to the pulse, from jerk (n.1) + -y (2). Related: Jerkily; jerkiness.
jeroboam (n.): type of large wine bottle, 1816, from Biblical name Jeroboam, "a mighty man of valour" (I Kings xi:28) "who made Israel to sin" (xiv:16), from Hebrew Yarobh'am, literally "let the people increase."
Jerome: masc. proper name, from French Jérome, from Late Latin Hieronymus, from Greek Hieronymos, literally "holy name," from hieros "holy" (see ire) + onyma, dialectal form of onoma "name" (see name (n.)).
Jerry (n.): World War I British Army slang for "a German; the Germans," 1919, probably an alteration of German based on the male nickname Jerry, popular form of Jeremy. But it also is said to be from the shape of the German helmet, which was thought to resemble a jerry, British slang for "chamber pot, toilet" (1850), this being probably an abbreviation of jeroboam, which is attested in this sense from 1827. Compare jerry-hat "round felt hat" (1841).
jerry-built (adj.): "built hastily of shoddy materials," 1856, in a Liverpool context, from jerry "bad, defective," probably a pejorative use of the male nickname Jerry (a popular form of Jeremy; compare Jerry-sneak "sneaking fellow, a hen-pecked husband" [OED], name of a character in Foote's "The Mayor of Garret," 1764). Or from or influenced by nautical slang jury (adj.) "temporary," which came to be used of all sorts of makeshift and inferior objects.
jerry-can (n.): "5-gallon metal container," 1943, from Jerry "a German." It was first used by German troops in World War II and later adopted by the Allies.
jersey (n.): 1580s as a type of knitted cloth; 1842 as a breed of cattle; both from Jersey, one of the Channel Islands. Its name is said to be a corruption of Latin Caesarea, the Roman name for the island (or another near it), influenced by Old English ey "island;" but it is perhaps rather a Viking name (perhaps meaning "Geirr's island").

The meaning "woolen knitted close-fitting tunic," especially one worn during sporting events, is from 1845. In American English, short for New Jersey from 1758. Related: Jerseyman.
Jerusalem: holy city in ancient Palestine, from Greek Hierousalem, from Hebrew Yerushalayim, literally "foundation of peace," from base of yarah "he threw, cast" + shalom "peace." Jerusalem "artichoke" is folk etymology of Italian girasole "sunflower" (see girasole).
jess (n.): leg-strap used in hawking and falconry, mid-14c., from Old French jes "straps fastened round the legs of a falcon," plural of jet, literally "a cast of a hawk, a throw, a throwing," from Latin iactus "a throw, a cast," from iacere "to throw, cast" (see jet (v.)). Related: Jesses.