Online Etymology Dictionary

amour (n.): c. 1300, "love," from Old French amour, from Latin amorem (nominative amor) "love, affection, strong friendly feeling" (it could be used of sons or brothers, but especially of sexual love), from amare "to love" (see Amy). The accent shifted 15c.-17c. to the first syllable as the word became nativized, then shifted back as the naughty or intriguing sense became primary and the word was felt to be a euphemism.
A common ME word for love, later accented ámour (cf. enamour). Now with suggestion of intrigue and treated as a F[rench] word. [Weekley]
amour-propre (n.): 1775, French, "sensitive self-love, self-esteem;" see amour and proper.
Vanity usually gives the meaning as well, &, if as well, then better. [Fowler]
The term was in Middle English as proper love "self-love."
amoxycillin (n.): 1971, contracted from amino- + oxy- + ending from penicillin.
Amoy: old name for the island of southeastern China, now known as Xiamen. From 1851 as the name of a dialect of Chinese.
amp (n.): 1886 as an abbreviation of ampere; 1967 as an abbreviation of amplifier.
amperage (n.): strength of an electric current, 1889, from ampere on model of voltage.
ampere (n.): 1881, "the current that one volt can send through one ohm," from French ampère, named for French physicist André-Marie Ampère (1775-1836). Shortened form amp is attested from 1886.
ampersand (n.): 1837, contraction of and per se and, meaning "(the character) '&' by itself is 'and' " (a hybrid phrase, partly in Latin, partly in English). The symbol is based on the Latin word et "and," and comes from an old Roman system of shorthand signs (ligatures), attested in Pompeiian graffiti, but not (as sometimes stated) from the Tironian Notes, which was a different form of shorthand, probably invented by Cicero's companion Marcus Tullius Tiro, which used a different symbol, something like a reversed capital gamma, to indicate et.

This Tironian symbol was maintained by some medieval scribes, including Anglo-Saxon chroniclers, who sprinkled their works with a symbol like a numeral 7 to indicate the word and. In old schoolbooks the ampersand was printed at the end of the alphabet and thus by 1880s had acquired a slang sense of "posterior, rear end, hindquarters."
amphetamine (n.): 1938, contracted from alphamethyl-phenethylamine.
amphi-: before a vowel amph-, word-forming element from Greek amphi- "both, of both kinds, on both sides, around," from amphi "round about, around;" cognate with Latin ambi- (see ambi-).
amphibian (adj.): 1630s, "having two modes of existence, of doubtful nature," from Greek amphibia, neuter plural of amphibios "living a double life," from amphi- "of both kinds" (see amphi-) + bios "life" (see bio-).

Formerly used by zoologists to describe all sorts of combined natures (including otters and seals), the biological sense "class of animals between fishes and reptiles that live both on land and in water" and the noun derivative both are first recorded 1835. Amphibia was used in this sense from c. 1600 and has been a zoological classification since c. 1819.
amphibious (adj.): 1640s, from Latinized form of Greek amphibios "having a double life" (see amphibian). Of motor vehicles, from 1915.
amphibrach (n.): 1580s, from Latin amphibrachus, from Greek amphibrakhys, name for a foot consisting of a long syllable between two short, literally "short at both ends," from amphi- "on both sides" (see amphi-) + brakhys "short" (see brief (adj.)).
Amphictyonic League: 1753, one of several ancient Greek confederations of neighboring states, from Greek amphiktionikos, from amphiktiones "neighbors," literally "they that dwell round about," from amphi- "on both sides" (see amphi-) + second element related to ktizein "to create, found," ktoina "habitation, township," from PIE root *tkei- "to settle, dwell, be home" (see home (n.)).
amphigory (n.): "burlesque nonsense writing or verse," 1809, from French amphigouri, which is of unknown origin, perhaps from Greek amphi- (see amphi-) + gyros "circle," thus "circle on both sides," or second element may be from Greek -agoria "speech" (compare allegory, category). Related: Amphigoric.
Amphiscians (n.): 1620s, from Medieval Latin Amphiscii, from Greek amphiskioi "inhabitants of the tropics," literally "throwing a shadow both ways," from amphi- "on both sides" (see amphi-) + skia "shadow" (see shine (v.)). Inhabitants of torrid zones, so called because they are "people whose shadow is sometimes to the North, and sometimes to the South" [Cockerham, 1623].
amphitheater (n.): late 14c., from Latin amphitheatrum, from Greek amphitheatron "double theater, amphitheater," neuter of amphitheatros "with spectators all around," from amphi- "on both sides" (see amphi-) + theatron "theater" (see theater). Classical theaters were semi-circles, thus two together made an amphi-theater.
amphitheatre (n.): chiefly British English spelling of amphitheater. See -er.
amphora (n.): early 14c., "two-handled vessel for holding wine, oil, etc.," from Latin amphora from Greek amphoreus "an amphora, jar, urn," contraction of amphiphoreus, literally "two-handled," from amphi- "on both sides" (see amphi-) + phoreus "bearer," related to pherein "to bear" (see infer). Also a liquid measure in the ancient world, in Greece equal to 9 gallons, in Rome to 6 gallons, 7 pints.
amphoteric (adj.): "neither acid nor alkaline," 1832, from Greek amphoteros "each or both of two," variant of amphi-.
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. Alternative stentorphone (1921) did not catch on.
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 "to 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," which is 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-Roman 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.," which is 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. (such as 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 (as in 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-).