Online Etymology Dictionary

ample (adj.): mid-15c., from Middle French ample, from Latin amplus "large, spacious," related to ampla "handle, grip."
amplification (n.): 1540s, "enlargement," from Latin amplificationem (nominative amplificatio) "a widening, extending," noun of action from past participle stem of amplificare (see amplify). Electronics sense is from 1915.
amplifier (n.): 1540s; agent noun from amplify. Electronic sense is from 1914; shortened form amp is from 1967.
amplify (v.): early 15c., "to enlarge or expand," from Middle French amplifier, from Latin amplificare "to enlarge," from amplificus "splendid," from amplus "large" (see ample) + the root of facere "make, do" (see factitious). Meaning "augment in volume or amount" is from 1570s. Restriction of use to sound seems to have emerged in the electronic age, c.1915, in reference to radio technology.
amplitude (n.): 1540s, from Middle French amplitude or directly from Latin amplitudinem (nominative amplitudo) "wide extent, width," from amplus (see ample). Amplitude modulation in reference to radio wave broadcast (as opposed to frequency modulation) first attested 1921, usually abbreviated a.m.
amply (adv.): 1550s, from ample + -ly (2).
ampoule (n.): "small bottle or flask," especially one used for holy liquids, c.1200, from Old French ampole, from Latin ampulla "small globular flask or bottle," of uncertain origin, perhaps a contracted form of amphora.
ampul (n.): sealed container holding a dose of medicine, 1907, from French ampul (1886), from Latin ampulla (see ampoule). A modern borrowing of the word represented by Middle English ampoule.
ampulla (n.): late 14c., type of globular ancient Roman vessel; see ampoule.
amputate (v.): 1630s, back-formation from amputation or else from Latin amputatus, past participle of amputare "to cut off, to prune." Related: Amputated; amputating.
amputation (n.): 1610s, "a cutting off of tree branches, a pruning," also "operation of cutting off a limb, etc., of a body," from Middle French amputation or directly from Latin amputationem (nominative amputatio), noun of action from past participle stem of amputare "cut off, lop off; cut around, to prune," from am(bi)- "about" (see ambi-) + putare "to prune, trim" (see pave).
amputee (n.): 1910, perhaps on a French model; see amputation + -ee.
Amsterdam: principal city of the Netherlands; the name is a reference to the dam built on the Amstel river. Prevalence of dam in Dutch place names reflects the geography of Holland.
amt (n.): territorial division in Denmark and Norway, from Danish amt, from German Amt "office," from Old High German ambaht, of Celtic origin, related to Gallo-Romance ambactus "servant" (see ambassador).
amtrac (n.): amphibious assault vehicle, 1944, from amphibious + tractor.
Amtrak: U.S. government-run railway corporation, 1971, contraction of American Track. Also is known as National Railway Passenger Corp.
amuck (adv.): 17c., variant of amok; treated as a muck by Dryden, Byron, etc., and defended by Fowler, who considered amok didacticism.
amulet (n.): mid-15c., amalettys, from Latin amuletum (Pliny) "thing worn as a charm against spells, disease, etc.," of uncertain origin, perhaps related to amoliri "to avert, to carry away, remove." Not recorded again in English until c.1600; the 15c. use may be via French.
amuse (v.): late 15c., "to divert the attention, beguile, delude," from Middle French amuser "divert, cause to muse," from a "at, to" (but here probably a causal prefix) + muser "ponder, stare fixedly" (see muse (v.)). Sense of "divert from serious business, tickle the fancy of" is recorded from 1630s, but through 18c. the primary meaning was "deceive, cheat" by first occupying the attention. Bemuse retains more of the original meaning. Related: Amused; amusing.
amusement (n.): c.1600, "diversion of attention," especially in military actions, from French amusement, noun of action from amuser (see amuse).
And because all bold and irreverent Speeches touching matters of high nature, and all malicious and false Reports tending to Sedition, or to the Amusement of Our People, are punishable ... (etc.) [Charles II, Proclamation of Oct. 26, 1688]
Meaning "a pastime, play, game, anything which pleasantly diverts the attention" (from duty, work, etc.) is from 1670s, originally depreciative; meaning "pleasurable diversion" attested from 1690s. Amusement hall is from 1862; amusement park first recorded 1897.
amusing (adj.): c.1600, "cheating;" present participle adjective from amuse (v.). Sense of "interesting" is from 1712; that of "pleasantly entertaining, tickling to the fancy" is from 1826. Noted late 1920s as a vogue word. Amusive has been tried in all senses since 18c. and might be useful, but it never caught on. Related: Amusingly.
Amy: fem. proper name, from Old French Amee, literally "beloved," from fem. past participle of amer "to love," from Latin amare, perhaps from PIE *am-a-, suffixed form of root *am-, a Latin and Celtic root forming various nursery words for "mother, aunt," etc. (cf. Latin amita "aunt").
amygdala (n.): "the tonsils," 1540s (amygdal), from Latin, from Greek amygdale "almond" (see almond). The anatomical use is as a direct translation of Arabic al-lauzatani "the two tonsils," literally "the two almonds," so called by Arabic physicians for fancied resemblance. From early 15c. as amygdales "tonsils;" as "almonds" from mid-12c.
amyl (n.): hydrocarbon radical, 1850, from Latin amylum, from Greek amylon "fine meal, starch," noun use of neuter of adjective amylos "not ground at the mill, ground by hand," from a-, privative prefix, "not" + myle "mill" (see mill (n.1)). So called because first obtained from the distilled spirits of potato or grain starch (though it also is obtained from other sources).
amylase (n.): enzyme which brings about the hydrolysis of starch, 1893, from amyl + chemical suffix -ase.
amyloid (adj.): "starch-like," 1857, coined in German (1839) from Latin amylum (see amyl) + Greek-derived suffix -oid. The noun is attested from 1872.
amyotrophic lateral sclerosis (n.): by 1881, from French, first word from Greek a-, privative prefix, + mys, myos "muscle" (see muscle (n.)) + trophikos "feeding," from trophe "nourishment" (see -trophy). Often known in U.S. as Lou Gehrig's disease, after the New York Yankees baseball player (1903-1941) who was diagnosed with it in 1939.
an: indefinite article before words beginning with vowels, 12c., from Old English an (with a long vowel) "one; lone," also used as a prefix an- "single, lone;" see one for the divergence of that word from this. Also see a, of which this is the older, fuller form.

In other European languages, identity between indefinite article and the word for "one" remains explicit (e.g. French un, German ein, etc.) Old English got by without indefinite articles: He was a good man in Old English was he wæs god man. Circa 15c., a and an commonly were written as one word with the following noun, which contributed to the confusion over how such words as newt and umpire ought to be divided (see N).

In Shakespeare, etc., an sometimes is a contraction of as if (a usage first attested c.1300), especially before it.
an- (1): privative prefix, from Greek an-, "not, without," related to ne- and cognate with Sanskrit an-, Latin in-, Gothic and Old English un- (see un- (1)).
an- (2): form of Latin ad- before -n- (see ad-).
ana-: before verbs an-, prefix meaning 1. "upward," 2. "back, backward, against," 3. "again, anew," from Greek ana- "up to, toward, exceedingly, back, against," from ana "up, on, upon, throughout, again," cognate with Old English on, from PIE root *ano- "on, upon, above" (see on).
anabaptism (n.): 1640s (as a Christian doctrine, with capital A-, from 1570s), from Medieval Latin anabaptismus, from Late Greek anabaptismos, from ana- "up (in place or time), back again, anew" (see ana-) + baptismos "baptism" (see baptism).
Anabaptist (n.): 1530s, "one who baptizes over again," from Modern Latin anabaptista, from Latin anabaptismus "second baptism" (used in literal sense from 4c.; see anabaptism).

Originally in English in reference to sect that practiced adult baptism and arose in Germany 1521. Probably so called because, as a new faith, they baptized converts who already had been baptized (as infants) in the older Christian churches. Modern branches only baptize once (adults) and do not actively seek converts. The name also was applied, usually opprobriously, to Baptists, perhaps due to the multiple immersions of their baptisms.
anabasis (n.): 1706, from Greek, "military expedition," literally "a going up (from the coast)," especially in reference to the advance of Cyrus the Younger from near the Aegean coast into Asia, and the subsequent story of the retreat of the 10,000 narrated by Xenophon (401 B.C.E.), from anabainein "to go up, mount;" from ana "up" (see ana-) + bainein "to go" (see come).
anabolic (adj.): "pertaining to the process of building up (especially in metabolism)," 1876, from Greek anabole "that which is thrown up; a mound," from anaballein "to throw or toss up," from ana "up, upward" (see ana-) + ballein "to throw" (see ballistics).
anabolism (n.): 1886; see anabolic + -ism.
anachronism (n.): 1640s, "an error in computing time or finding dates," from Latin anachronismus, from Greek anakhronismos, from anakhronizein "refer to wrong time," from ana- "against" (see ana-) + khronos "time" (see chrono-). Meaning "something out of harmony with the present" first recorded 1816.
anachronistic (adj.): 1775; see anachronism + -istic.
anacoluthon (n.): "want of grammatical sequence; changing constructions in mid-clause," 1706, from Latinized form of Greek anakoluthon, neuter of anakolouthos "inconsequent," from an- "not" (see an- (1)) + akolouthos "following," from copulative prefix a- + keleuthos "way, road, track, path" (see celerity).
anaconda (n.): 1768, a name first used in English to name a Ceylonese python, it was applied erroneously to a large South American boa, called in Brazil sucuriuba. The word is of uncertain origin, and no snake name like it now is found in Sinhalese or Tamil. One suggestion is that it is a Latinization of Sinhalese henacandaya "whip snake," literally "lightning-stem" [Barnhart]. Another suggestion is that it represents Tamil anaikkonda "having killed an elephant" [OED].
Anacreontic (adj.): of or in the manner of Anacreon, "convivial bard of Greece" (literally "Up-lord"), the celebrated Greek lyrical poet (560-478 B.C.E.), born at Teos in Ionia. Also in reference to his lyric form (1706) of a four-line stanza, rhymed alternately, each line with four beats (three trochees and a long syllable), also "convivial and amatory" (1801); and "an erotic poem celebrating love and wine" (1650s).

Francis Scott Key in 1814 set or wrote his poem "The Star-Spangled Banner" to the melody of "To Anacreon in Heav'n," the drinking song of the popular London gentleman's club called The Anacreontic Society, whose membership was dedicated to "wit, harmony, and the god of wine." The tune is late 18c. and may be the work of society member and court musician John Stafford Smith (1750-1836).
anacrusis (n.): "unstressed syllable at the beginning of a verse," 1833, Latinized from Greek anakrousis "a pushing back," of a ship, "backing water," from anakrouein "to push back, stop short, check," from ana- "back" (see ana-) + krouein "to strike," from PIE *kreue- (2) "to push, strike" (cf. Russian krusit, Lithuanian krusu "to smash, shatter," Old Church Slavonic kruchu "piece, bit of food," Old English hreowian "feel pain or sorrow," Old Norse hryggja "make sad").
anadiplosis (n.): "repetition of an initial word," 1580s, from Latin, from Greek anadiplosis, from anadiploesthai "to be doubled back, to be made double," from ana "back" (see ana-) + diploun "to double, fold over" (see diploma).
anadromous (adj.): of fish, "ascending a river to spawn" (as salmon do), 1753, from Latinized form of Greek anadromos "running upward," from ana "up, back" (see ana-) + dramein "to run" (see dromedary).
anaemia (n.): 1824, from French medical term (1761), Modern Latin, from Greek anaimia "lack of blood," from anaimos "bloodless," from an- "without" (see an- (1)) + haima "blood" (see -emia).
anaemic (adj.): c.1840; see anaemia + -ic. Figurative sense by 1898.
anaerobic (adj.): "capable of living without oxygen," 1879 (as anaerobian; modern form first attested 1884), from French anaérobie, coined 1863 by French bacteriologist Louis Pasteur (1822-1895), from Greek an- "without" (see an- (1)) + aer "air" (see air (n.1)) + bios "life" (see bio-).
anaesthesia (n.): 1721, "loss of feeling," Modern Latin, from Greek anaisthesia "want of feeling, lack of sensation (to pleasure or pain)," from an- "without" (see an- (1)) + aisthesis "feeling," from PIE root *au- "to perceive" (see audience). As "a procedure for the prevention of pain in surgical operations," from 1846.
anaesthesiologist (n.): 1943, American English, from anaesthesiology + -ist.
anaesthesiology (n.): 1908, from anaesthesia + -ology.
Anesthesiology. This is the new term adopted by the University of Illinois defining "the science that treats of the means and methods of producing in man or animal various degrees of insensibility with or without hypnosis." ["Medical Herald," January, 1912]