Online Etymology Dictionary

Rotwelsch (n.): "jargon of thieves and vagabonds," 1841, from German Rotwelsch, literally "Red Welsh," from rot (see red (adj.1)) + Welsh because obscure and difficult. But the first element may be connected with Middle High German rot "beggar."
radio-: word-forming element meaning 1. "ray, ray-like" (see radius); 2. "radial, radially" (see radial (adj.)); 3. "by means of radiant energy" (see radiate (v.)); 4. "radioactive" (see radioactive); 5. "by radio" (see radio (n.)).
rat-tail (n.): also rat's-tail, used since 16c. of conditions or devices held to resemble a rat's long, hairless tail in some sense, including "lank lock of hair" (1810); "end of a rope" (1867); from rat (n.) + tail (n.1).
shocking (adj.): 1690s, "offensive," present participle adjective from shock (v.1). From 1704 as "causing a jolt of indignation, horror, etc.;" from 1798 as "so bad as to be shocking." Related: Shockingly. Shocking pink introduced February 1937 by Italian-born fashion designer Elsa Schiaparelli.
snowbird (n.): also snow-bird, from 1680s in reference to various types of birds associated with snow, from snow (n.) + bird (n.1). From 1923 in reference to northern U.S. workers who went to the South in the winter months to work; by 1979 in reference to tourists.
stool-ball (n.): outdoor game similar to cricket, in 16c. and 17c. generally played by women alone, late 15c., from stool (n.) + ball (n.1). "The 'stool' was the wicket ... perhaps it was originally an ordinary stool" [OED].
split-second (n.): 1884, originally the name of a type of stopwatch with two second hands that could be stopped independently. Meaning "a fraction of a second" is from 1912, from split (adj.) + second (n.1); adjectival meaning "occurring in a fraction of a second" is from 1946.
deport (v.2): "banish," 1640s, from French déporter, from Latin deportare "carry off, transport, banish, exile," from de- in its sense of "off, away" (see de-) + portare "to carry" (but associated by folk etymology with portus "harbor"); see port (n.1). Related: Deported; deporting.
Theropoda (n.): order of dinosaurs, Modern Latin, from Greek elements ther- "beast" + podos genitive of pous "foot," from PIE root *ped- (1) "a foot" (see foot (n.)). So called because the structure of the feet resembled quadrupeds rather than birds. Related: Theropod.
thunderbird (n.): legendary cause of thunder in many Native American cultures, 1848, a translation of native words, such as Ojibwa (Algonquian) aninikii, Lakotah (Siouan) wakiya, Klamath /lmelmnis/. See thunder (n.) + bird (n.1). In Lakhota, "the thunderbirds call" is "the usual expression for thunder" [Bright].
fire-drill (n.): 1865, originally a device for making fire by the twirled stick method, from fire (n.) + drill (n.1). Meaning "rehearsal of what to do in a fire" is from 1884 (originally it also involved fighting the fire), from drill (n.) in the "agreed-upon procedure" sense (see drill (v.)).
flash (n.2): "sudden rush of water," 1660s, earlier "watery place or marsh, a swamp" (c. 1400; in place names from c. 1300), of uncertain origin or connection to flash (n.1); perhaps from Old French flache, from Middle Dutch vlacke. Flash flood is from 1940.
vamp (n.1): "upper of a shoe or boot," 1650s, earlier "part of a stocking that covers the foot and ankle" (c. 1200), from Anglo-French *vaumpé, from Old French avantpié "vamp of a shoe," from avant "in front" (see avant) + pié "foot," from Latin pes, from PIE root *ped- (1) "a foot" (see foot (n.)).
fugleman (n.): also fugelman, "expert soldier placed in front of a regiment or company in exercises as an example to the others," a mangled borrowing of German Flügelmann "leader of a file," literally "wing-man," from Flügel "wing" (related to fliegen "to fly;" see fly (v.1)) + Mann (see man (n.)).
wingtip (n.): also wing-tip, 1867, "tip of a wing" (originally of insects; by 1870 of birds), from wing (n.) + tip (n.1). Of airplane wings from 1909. As a type of shoe with a back-curving toe cap suggestive of a bird's wingtip, from 1928. Related: Wing-tipped.
fag (v.2): "put to work at certain duties, compel to work for one's benefit," 1806, from British public school slang fag (n.) "junior student who does certain duties for a senior" (1785), from fag (v.1). Related: Fagdom (1902); faggery "fatiguing labor" (1853).
ear-worm (n.): 1880, "boll-worm, corn parasite" (corn-ear-worm attested from 1855), from ear (n.2) + worm (n.). Also an old alternative name for "earwig" (from ear (n.1)); from 1881 as "secret counselor." From 1989 as "annoyingly unforgettable pop song or part of a song."
weave (v.2): c. 1200, "to move from one place to another," of uncertain origin, perhaps from weave (v.1). From early 14c. as "move to and fro;" 1590s as "move side to side." Use in boxing is from 1818. Related: Weaved; weaving.
informed (adj.): 1540s, "current in information," past-participle adjective from inform (v.). In 16c.-17c. it also could mean "unformed, formless," from in- (1) "not, opposite of," and was used in astronomy of stars that did not form part of the visual pattern of a constellation but were within it.
inofficious (adj.): c. 1600, "neglecting one's duty;" in law, "not in accord with one's moral duty," 1660s, from Medieval Latin inofficiosus "contrary to duty; harmful," from in- "not, opposite of" (see in- (1) + Latin officiosus "dutiful, obliging" (see officious).
incensed (adj.): "full of wrath, inflamed with anger," 1590s, past-participle adjective from incense (v.1). Earlier it was used in heraldry, in reference to fire-breathing animals (1570s). Distinguished in pronunciation from incensed "perfumed witrh incense" (1610s), from incense (v.2).
incondite (adj.): 1630s, "ill-made," earlier "crude, upolished" (1530s), from Latin inconditus "disordered, uncouth," from in- "not, opposite of" (see in- (1)) + conditus, past participle of condere "put together" (see abscond). Applied from 1845 to natural utterances ("oh!") from Latin (vox) incondita.
Herodian (adj.): pertaining to Herod, name of rulers in ancient Palestine in Roman times, especially Herod the Great, king of Judea 38-4 B.C.E. The name is Greek, Herodes, from heros "hero" (see hero (n.1)) + patronymic suffix -des.
key (adj.): "crucially important," 1913, from key (n.1). Perhaps from or reinforced by key move, in chess, "first move in a solution to a set problem" (1827), which to an experienced player opens the way to see how the solution will develop.
lede (n.1): by 1965, alternative spelling of lead (n.2) in the newspaper journalism sense, to distinguish this specialized sense from other possible meanings of the written word, perhaps especially the molten lead (n.1) used in 20c. typesetting machines.
leading (adj.): 1590s, "that goes first," present participle adjective from lead (v.1). Meaning "directing, guiding" is from 1620s. Of persons, "having first or most prominent place," 1670s. In reference to theatrical companies, leading lady is from 1846; leading man from 1847.
letter-head (n.): also letterhead, "sheet of paper with a printed or engraved logo or address," 1868, short for letterheading (1867); from letter (n.1) + heading (n.) in the printing sense. So called because it was printed at the "head" of the sheet of paper.
letter-opener (n.): 1864 as a device to slit open letter envelopes, from letter (n.1) + opener. Earlier as a government or other official on continental Europe in charge of opening and reading private mails of suspected persons and censoring them (1847).
lighten (v.2): "shed light upon, illuminate, make light or bright," early 14c., from light (n.) -en (1). Intransitive meaning "to become brighter" is late 14c.; of faces, expressions, etc., from 1795. Meaning "to flash lightning" is from mid-15c. Related: Lightened; lightening.
lightweight (adj.): also light-weight, 1809, from the noun (1773 in horse-racing, also in pugilism), "man or animal of a certain weight prescribed by rule," from light (adj.1) + weight (n.). Figurative sense of "inconsequential" first attested 1809. The noun sense of "person of little importance or accomplishment" is from 1885.
ligni-: sometimes ligno-, word-forming element used from late 19c. and meaning "wood," from Latin lignum "wood (for fuel or construction), firewood," from PIE *leg-no-, literally "that which is collected," from root *leg- (1) "to collect" (see lecture (n.)). Related: Lignify; lignification.
link (v.): "to bind, fasten, couple, unite as if by links," late 14c., believed to be from link (n.1), though it is attested earlier. Intransitive sense "become connected, join in marriage" is from 1530s. Related: Linked; linking.
list (v.3): "to put down in a list or catalogue; to make a list of," 1610s, from list (n.1). Meaning "to place real estate on the market" is from 1904. Meaning "put an edge around" (c. 1300, now probably obsolete) is from Old French lister or else from list (n.2). Related: Listed; listing.
litterateur (n.): "a literary man, one whose profession is literature," 1806, from French littérateur, from Latin litterator "a grammarian, philologist," from littera "letter; writing" (see letter (n.1)). Sometimes Englished as literator (1630s), but often with a deprecatory sense. O.W. Holmes used or coined the fem. form littératrice (1879).
llano (n.): 1610s, American Spanish, "prairie; treeless, level plain," especially that of South America north of the Amazon, from noun use of Spanish llano "plain, even, level, smooth," ultimately from Latin planus "smooth" (see plane (n.1)). Hence llanero "Latin-American cowboy" (1819), literally "plainsman."
rocky (adj.): "full of rocks," c. 1400, from rock (n.1) + -y (2); "unsteady," 1737, from rock (v.1). Meaning "difficult, hard" is recorded from 1873, and may represent a bit of both.

The Rocky Mountains so called by 1802, translating French Montagnes Rocheuses, first applied to the Canadian Rockies. "The name is not directly self-descriptive but is an approximate translation of the name of the former Native American people here known as the Assiniboin .... The mountains are in fact not noticeably rocky" [Room]. Bright notes that "These Indians were called /assiniipwaan/, lit. 'stone Sioux', by their Cree (Algonkian) neighbors".
blow job (n.): also blowjob, 1961, from blow + job. Exactly which blow is meant is the subject of some debate; the word might have begun as a euphemism for suck (thus from blow (v.1)), or it might refer to the explosive climax of an orgasm (thus blow (v.2)). Unlike much sex slang, its date of origin probably is pretty close to the date it first is attested in print: as recently as the early 1950s, military pilots could innocently talk of their jet planes as blow jobs according to the "Thesaurus of American Slang." Compare blow (v.1).
backward (adv.): c. 1300, from abakward, from Old English on bæc (see back (adv.)) + -weard adjectival and adverbial suffix (see -ward). Old English had the adverb bæcling. As an adjective, from 1550s. Meaning "behindhand with regard to progress" is first attested 1690s. To ring bells backward (from lowest to highest), c. 1500, was a signal of alarm for fire or invasion, or to express dismay. Another Middle English word for "backward, wrongly" was arseward (c. 1400); Old English had earsling.
Danish: Old English Denisc "people of Denmark" (see Dane); danish pastry is 1934; shortened form danish is from 1963.
cumin (n.): Old English cymen, from Latin cuminum, from Greek kyminon, cognate with Hebrew kammon, Arabic kammun.
cute (adj.): 1731, "clever," shortening of acute; informal sense of "pretty" is 1834, American English student slang. Related: Cuteness.
cyst (n.): 1713, from Modern Latin cystis (in English as a Latin word from 1540s), from Greek kystis "bladder, pouch."
cagey (adj.): "evasive, reticent," 1896, U.S. colloquial, of unknown origin. Earlier in English dialect it meant "sportive."
croft (n.): Old English croft "enclosed field, small field," of unknown etymology. Crofter is 1799, originally Scottish.
cruller (n.): 1805, American English, apparently from Dutch kruller, from krullen "to curl," from Middle Dutch crullen, related to curl.
crumple (v.): c. 1300, crumplen, frequentative of crumpen "to curl up" (from Old English crump "bent, crooked"). Related: Crumpled; crumpling.
cudgel (n.): Old English cycgel "club with rounded head;" perhaps from PIE root *geu- "to curve, bend."
decolletage (n.): 1894 (from 1883 as a French word in English), from French décolletage, from décolleté "low-necked" (see decollete).
decolonization (n.): 1853 in political sense, American English, from de- + colonization. Earlier as a medical term.
eft (n.): Old English efte, efeta "small lizard-like animal," of unknown origin (see newt).