Online Etymology Dictionary

tropical (adj.): 1520s, "pertaining to the celestial tropics," from tropic + -al (1). In reference to the torrid zones of the earth, from 1690s. Meaning "hot and lush like the climate of the tropics" is first attested 1834.
trooper (n.): 1630s, "soldier in a cavalry troop," from troop (n.) + -er (1). Extended to "mounted policeman" (1858, in Australia) then to "state policeman" (U.S.) by 1911.
untouched (adj.): late 14c., "not been physically contacted," from un- (1) "not" + past participle of touch (v.). Meaning "unharmed, uninjured" is from c. 1400; that of "not used at all" is from 1530s; sense of "unmoved emotionally" is from 1610s.
unutterable (adj.): 1580s, from un- (1) "not" + utterable (see utter (v.)). As a noun, from 1788; unutterables as a euphemism for "trousers" is recorded by 1826 (see inexpressible).
tiptoe (n.): late 14c., from tip (n.1) + toe (n.). As an adverb from 1590s; as a verb from 1630s. Related: Tiptoes (late 14c.), also tiptoon; tip-toed. Tippy-toes is from 1820.
vitiligo (n.): 1650s, from Latin vitiglio "a kind of cutaneous eruption, tetter" (Celsus), perhaps with an original sense of "blemish," from PIE *wi-tu-, from root *wei- (3) "vice, fault, guilt" (see vice (n.1)).
whirligig (n.): mid-15c., a child's toy, from whirl (v.) + gig (see gig (n.1)). Meaning "anything in constant motion" is from 1580s; "fickle, flighty person" is from c. 1600; as a type of water beetle, from 1713.
aero-: word-forming element meaning "air, atmosphere; aircraft; gases," from Greek aero-, comb. form of aer (genitive aeros) "air, lower atmosphere" (see air (n.1)).
hydro-: before vowels hydr-, word-forming element in compounds of Greek origin, meaning "water," from Greek hydro-, comb. form of hydor "water" (see water (n.1)). Also sometimes a comb. form of hydrogen.
glue-pot (n.): late 15c., from glue (n.) + pot (n.1). Typically a double pot, one within the other, the inner one for the glue, the outer for the hot water.
adversarial (adj.): by 1892, from adversary + -al (1). Probably coined to avoid confusion which might arise with use of adversary (adj.), which is attested from late 14c. Related: Adversarially.
top-hamper (n.): 1791, originally the upper masts, sails, and rigging of a sailing ship, from top (n.1) + hamper (n.) in the nautical sense of "things necessary but often in the way."
Adamite (n.): "human being, descendant of Adam" the Biblical first man, 1630s, from Adam + -ite (1). Used from 1620s in reference to sects or groups that practice nudism, in reference to the state of Adam before the Fall.
air (v.): "to expose to open air," 1520s, from air (n.1). Figurative sense of "to expose, make public" is from 1610s of objects, 1862 of opinions, grievances, etc. Meaning "to broadcast" (originally on radio) is from 1933. Related: Aired; airing.
game-cock: cock bred for fighting or from fighting stock, 1670s, from game (n.) in the sporting and amusement sense + cock (n.1). Figurative use by 1727.
gas-house (n.): also gashouse, 1880 as a power-generating station, from gas (n.1) + house (n.). By 1926, emblematic of a run-down district of a U.S. city, a typical abode of criminals and gangsters.
porte-cochere (n.): gateway for carriages, 1690s, from French porte-cochère, from porte "gate" (from PIE root *per- (2) "to lead, pass over;" see port (n.1)) + cochère, fem. adjective from coche "coach" (see coach (n.)).
Hamite (n.): 1854, "a descendant of Biblical Ham" (see Hamitic), with -ite (1). Used in reference to Egyptian and other peoples of north and northeast Africa; but popularly, "a black African, a negro."
Hildegard: Germanic fem. proper name, Old High German Hildegard, literally "protecting battle-maid;" for first element see Hilda; for second element see yard (n.1).
-ial: adjectival word-forming element, variant of -al (1) with connective -i-. From Latin -ialis, in which the -i- originally was from the stem of the word being attached but later came to be felt as connective.
impassionate (adj.): "free from passion, dispassionate," 1620s, from in- (1) "not" + passionate. Related: Impassionately. From 1590s as "strongly affected, stirred by passion," from Italian impassionato, past participle of impassionare (see impassion).
incombustible (adj.): "incapable of being burned or consumed by fire," late 15c., from Old French incombustible (14c.) or directly from Medieval Latin incombustibilis; see in- (1) + combustible. As a noun from 1807. Related: Combustibility.
indigestible (adj.): late 15c., from Late Latin indigestibilis or else a native formation from in- (1) "not, opposite of" + digestible; or else from Late Latin indigestibilis. Related: Indigestibility (1733).
inexpert (adj.): mid-15c., from in- (1) "not, opposite of" + expert (adj.), or else from Old French inexpert or directly from Latin inexpertus "without experience, unpracticed; untried, untested." Related: Inexpertly.
armless (adj.): late 14c., of physical conditions, from arm (n.1) + -less. Meaning "without weapons" is attested from 1610s (from arm (n.2)), but that sense is more typically expressed by unarmed.
arthro-: word-forming element meaning "pertaining to the joints," from Greek arthro- (before vowels arth-), comb. form of arthron "joint," from PIE *ar-dhro-, from *ar- "to fit together;" see arm (n.1).
halo-: before vowels hal-, word-forming element meaning "salt, sea," from Greek hals (genitive halos) "a lump of salt, salt generally," in Homer, "the sea," from PIE *sal- (1) "salt" (see salt (n.)).
hali-: word-forming element meaning "salt, a lump of salt," from Greek hali-, comb. form of hals (genitive halos) "a lump of salt, salt generally," and in Homer, "the sea," from PIE *sal- (1) "salt" (see salt (n.)).
blacken (v.): c. 1200, "become black or dark;" early 14c., "make black, darken, dye (hair);" see black + -en (1). Figurative sense of "to besmirch" (with dishonor, etc.) is from early 15c. Related: Blackened; blackening.
hendeca-: word-forming element meaning "eleven," from Latinized form of Greek hendeka "eleven," from hen, neuter of heis "one," from PIE *hems-, from root *sem- (1) "one" (see same) + deka "ten" (see ten).
impassive (adj.): 1660s, "not feeling pain, insen" from assimilated form of in- "not, opposite of" (see in- (1)) + passive. Meaning "void of emotions, unmoved" is from 1690s. Related: Impassively; impassiveness (1640s).
importunate (adj.): 1520s, from importune + -ate (1), or else from Medieval Latin importunatus, past participle of importunari "to make oneself troublesome." Related: Importunately (mid-15c.). Earlier adjective was importune (c. 1400).
equivocal (adj.): c. 1600, from Late Latin aequivocus "of equal voice, of equal significance, ambiguous" (see equivocation) + -al (1). Earlier in same sense was equivoque (late 14c.). Related: Equivocally (1570s).
functional (adj.): 1630s, "pertaining to function or office," from function (n.) + -al (1), or from Medieval Latin functionalis. Meaning "utilitarian" is by 1864; specific use in architecture is from 1928. Related: Functionally; functionality.
incoherent (adj.): 1620s, "without coherence" (of immaterial or abstract things, especially thought or language), from in- (1) "not, opposite of" + coherent. As "without physical coherence" from 1690s. Related: Incoherently.
incredulous (adj.): "unbelieving," 1570s, from Latin incredulus "unbelieving, incredulous," from in- "not" (see in- (1)) + credulus (see credulous). Formerly also of religious beliefs. Related: Incredulously; incredulousness.
insouciant (adj.): 1828, from French insouciant "careless, thoughtless, heedless," from in- "not" (see in- (1)) + souciant "caring," present participle of soucier "to care," from Latin sollicitare "to agitate" (see solicit). Related: Insouciantly.
interpose (v.): 1590s (trans.); 1610s (intrans.), from Middle French interposer (14c.), from inter- "between" (see inter-) + poser "to place" (see pose (v.1)). Related: Interposed; interposing.
logical (adj.): early 15c., "based on reason," from logic + -al (1). Meaning "pertaining to logic" is c. 1500. Attested from 1860 as "following as a reasonable consequence." Related: Logically.
abyssal (adj.): 1690s, used especially of the zone of ocean water below 300 fathoms, from abyss + -al (1). Though the 19th century, abysmal was more common in oceanography.
lawn-mower (n.): 1853 as a type of machine to cut grass, from lawn (n.1) + mower. Originally pushed by hand or drawn by horses, later also powered by a motor.
potboiler (n.): also pot-boiler, 1864 in the figurative literary sense, from pot (n.1) + agent noun from boil (v.). The notion is of something one writes solely to put food on the table.
national (adj.): 1590s, from Middle French national (from Old French nation), and also from nation + -al (1). As a noun, "citizen of a (particular) nation," from 1887. National anthem first recorded 1819, in Shelley. Related: Nationally.
epidural (adj.): 1873, "situated on or affecting the dura mater," from epi- "on" + dura mater + -al (1). The noun meaning "injection into the epidural region" (usually given during childbirth) is attested by 1966.
freehold (n.): "landed estate in possession of a freeman," late 15c., later generalized to any outright ownership of land, a translation of Anglo-French fraunc tenement; see free (adj.) + hold (n.1).
freezer (n.): 1847 as the name of a type of large tin can used in ice-cream manufacture; from freeze (v.) + -er (1). As a household appliance, from 1945. Freezer burn attested from 1929.
funereal (adj.): "suitable for a funeral" (mournful, dismal, gloomy), 1725, from stem of Latin funereus "of a funeral," from funus "funeral; death" (see funeral) + -al (1). Perhaps by influence of Middle French funerail.
flywheel (n.): also fly-wheel, "heavy-rimmed revolving wheel to regulate motion," 1784, from fly (n.) "speed-regulating device" (1590s, from fly (v.1)) + wheel (n.).
inseparability (n.): 1620s, from Late Latin inseparabilitas "inseparableness," from Latin inseparabilis "that cannot be separated," from in- "not, opposite of" (see in- (1)) + separabilis, from separare (see separate (v.)).
invalidity (n.): 1540s, from Middle French invalidité (16c.) or directly from Medieval Latin invaliditas "weakness, infirmity," from Latin invalidus "not strong, weak, feeble" (see invalid (adj.1)).