Online Etymology Dictionary

Aubrey: masc. personal name, from Old French Auberi, from Old High German Alberich "ruler of elves," or *Alb(e)rada "elf-counsel" (fem.). In U.S., it began to be used as a girl's name c.1973 and was among the top 100 given names for girls born 2006-2008, eclipsing its use for boys, which faded in proportion.
auburn (n.): early 15c., from Old French auborne, from Medieval Latin alburnus "off-white, whitish," from Latin albus "white" (see alb). It came to English meaning "yellowish-white, flaxen," but shifted 16c. to "reddish-brown" under influence of Middle English brun "brown," which also changed the spelling.
auction (n.): "a sale by increase of bids," 1590s, from Latin auctionem (nominative auctio) "an increasing sale, auction, public sale," noun of action from past participle stem of augere "to increase," from PIE root *aug- "to increase" (see augment). In northern England and Scotland, called a roup. In the U.S., something is sold at auction; in England, by auction.
auction (v.): 1807, from auction (n.). Related: Auctioned; auctioning.
auctioneer: 1708 as a noun; 1733 as a verb; see auction + -eer.
audacious (adj.): 1540s, "confident, intrepid," from Middle French audacieux, from audace "boldness," from Latin audacia "daring, boldness, courage," from audax "brave, bold, daring," but more often "bold" in a bad sense, "audacious, rash, foolhardy," from audere "to dare, be bold." Bad sense of "shameless" is attested from 1590s in English. Related: Audaciously.
audacity (n.): mid-15c., from Medieval Latin audacitas "boldness," from Latin audacis genitive of audax (see audacious).
audible (adj.): 1520s, from Middle French audible and directly from Late Latin audibilis, from Latin audire "to hear," from PIE *awis-dh-yo-, from root *au- "to perceive" (see audience). Related: Audibly.
audience (n.): late 14c., "the action of hearing," from Old French audience, from Latin audentia "a hearing, listening," from audientum (nominative audiens), present participle of audire "to hear," from PIE compound *au-dh- "to perceive physically, grasp," from root *au- "to perceive" (cf. Greek aisthanesthai "to feel;" Sanskrit avih, Avestan avish "openly, evidently;" Old Church Slavonic javiti "to reveal"). Meaning "formal hearing or reception" is from late 14c.; that of "persons within hearing range, assembly of listeners" is from early 15c. (French audience retains only the older senses). Sense transferred 1855 to "readers of a book." Audience-participation (adj.) first recorded 1940.
audio (n.): "sound," especially recorded or transmitted, 1934, abstracted from prefix audio- (in audio-frequency, 1919, etc.), from Latin audire "hear" (see audience).
audio-: word-forming element meaning "sound, hearing," from comb. form of Latin audire "hear," (see audience); first used in English as a word-formation element 1913.
audiology (n.): science of hearing and treatment of deafness, 1946, from audio- + -ology. Related: Audiologist.
audiophile (n.): 1951, originally in "High Fidelity" magazine, from audio- + -phile.
audiotape (n.): 1957, from audio- + tape (n.).
audiovisual (adj.): 1937 (also audio-visual), from audio- + visual.
audit (n.): early 15c., from Latin auditus "a hearing," past participle of audire "hear" (see audience). Official examination of accounts, which originally was an oral procedure.
audit (v.): mid-15c., from audit (n.). Related: Audited; auditing.
audition (v.): "to try out for a performance part," 1935, from audition (n.). Transitive sense by 1944. Related: Auditioned; auditioning.
audition (n.): 1590s, "power of hearing," from Middle French audicion "hearing (in a court of law)," from Latin auditionem (nominative auditio) "a hearing, listening to," noun of action from past participle stem of audire "hear" (see audience). Meaning "trial for a performer" first recorded 1881.
auditor (n.): early 14c., "official who receives and examines accounts;" late 14c., "a listener," from Anglo-French auditour (Old French oieor "listener, court clerk," 13c.; Modern French auditeur), from Latin auditor "a hearer," from auditus, past participle of audire "to hear" (see audience). Meaning "receiver and examiner of accounts" is because this process formerly was done, and vouched for, orally.
auditorium (n.): 1727, from Latin auditorium "lecture room," literally "place where something is heard," neuter of auditorius (adj.) "of or for hearing," from auditus, past participle of audire "to hear" (see audience); also see -ory. Earlier in the same sense was auditory (late 14c.).
auditory (adj.): 1570s, from Latin auditorius "pertaining to hearing," from auditor "hearer" (see auditor).
Audrey: fem. proper name, contracted from Etheldreda, a Latinized form of Old English Æðelðryð, literally "noble might," from æðele "noble" (see atheling) + ðryð "strength, might."
Audubon: with reference to birds or pictures of them, from U.S. naturalist John James Audubon (1785-1851).
Aufklarung (n.): 1801, from German Aufklärung (18c.), literally "Enlightenment," from aufklären "to enlighten" (17c.), from auf "up" + klären "to clear," from Latin clarus (see clear (adj.)).
Augean (adj.): "filthy," 1590s, in reference to Augean stable, the cleansing of which was one of the labors of Herakles, from Greek Augeias, like the stable of Augeas, king of Elis, which contained 3,000 oxen and had gone uncleansed for 30 years. Herakles purified it in one day by turning the river Alpheus through it.
auger (n.): c.1500, faulty separation of Middle English a nauger, from Old English nafogar "nave drill," from Proto-Germanic *nabogaizaz (cf. Old Norse nafarr, Old Saxon nabuger, Old High German nabuger), a compound whose first element is related to nave (n.2) and whose second is identical to Old English gar "a spear, borer" (see gar). For similar misdivisions, see adder. The same change took place in Dutch (avegaar).
aught (n.1): "something," Old English awiht "aught, anything, something," literally "e'er a whit," from Proto-Germanic *aiwi "ever" (from PIE *aiw- "vital force, life, long life, eternity;" see eon) + *wihti "thing, anything whatever" (see wight). In Shakespeare, Milton and Pope, aught and ought occur indiscriminately.
aught (n.2): "nothing, zero," faulty separation of a naught (see naught; cf. also adder for the separation problem).
augment (v.): c.1400, from Old French augmenter "increase, enhance" (14c.), from Late Latin augmentare "to increase," from Latin augmentum "an increase," from augere "to increase, make big, enlarge, enrich," from PIE root *aug- "to increase" (cf. Sanskrit ojas- "strength;" Lithuanian augu "to grow," aukstas "high, of superior rank;" Greek auxo "increase," auxein "to increase;" Gothic aukan "to grow, increase;" Old English eacien "to increase"). Related: Augmented; augmenting. As a noun from early 15c.
augmentation (n.): mid-15c., "act of making greater," from Old French augmentacion "increase," from Late Latin augmentationem (nominative augmentatio), noun of action from past participle stem of augmentare (see augment). Meaning "amount by which something is increased" is from 1520s. Musical sense is from 1590s.
augmentative (adj.): c.1500, from Middle French augmentatif (14c.), from Latin augmentat-, stem of augmentare (see augment).
augmented (adj.): past participle adjective from augment, c.1600. Musical sense is attested from 1825.
augur (n.): 1540s, from Latin augur, a religious official in ancient Rome who foretold events by interpreting omens, perhaps originally meaning "an increase in crops enacted in ritual," in which case it probably is from Old Latin *augos (genitive *augeris) "increase," and is related to augere "increase" (see augment). The more popular theory is that it is from Latin avis "bird," because the flights, singing, and feeding of birds, along with entrails from bird sacrifices, were important objects of divination (cf. auspicious). In that case, the second element would be from garrire "to talk."
augur (v.): c.1600, from augur (n.). Related: Augured; auguring.
augury (n.): late 14c., "divination from the flight of birds," from Old French augure "divination, soothsaying, sorcery, enchantment," or directly from Latin augurium "divination, the observation and interpretation of omens" (see augur). Figurative sense of "omen, portent, indication" is from 1797 (also often in plural as auguries).
august (adj.): 1660s, from Latin augustus "venerable, majestic, magnificent, noble," probably originally "consecrated by the augurs, with favorable auguries" (see augur (n.)); or else "that which is increased" (see augment).
August: eighth month, 1097, from Latin Augustus (mensis), sixth month of the later Roman calendar, renamed from Sextilis in 8 B.C.E. to honor emperor Augustus Caesar, literally "Venerable Caesar" (see august (adj.)). In England, the name replaced native Weodmonað "weed month."
Augusta: fem. proper name, Latin fem. of Augustus.
Augustan (adj.): 1640s, from Latin Augustanus, "pertaining to Augustus (Caesar)," whose reign was connected with "the palmy period of Latin literature" [OED]; hence, "period of purity and refinement in any national literature" (1712).
Augustine (adj.): c.1400 in reference to members of the religious order named for St. Augustine the Great (354-430), bishop of Hippo.
Augustus: masc. proper name, from Latin augustus "venerable" (see august). The name originally was a cognomen applied to Gaius Julius Caesar Octavianus as emperor, with a sense something like "his majesty."
auk (n.): 1670s, from a Scandinavian source, cf. Old Norse alka, probably originally imitative of a water-bird cry (cf. Latin olor "swan," Greek elea "marsh bird").
auld (adj.): variant of old that more accurately preserves the Anglo-Saxon vowel. Surviving in northern English and Scottish; distinctly Scottish after late 14c.
aunt (n.): c.1300, from Anglo-French aunte, Old French ante (Modern French tante, from a 13c. variant), from Latin amita "paternal aunt" diminutive of *amma a baby-talk word for "mother" (cf. Greek amma "mother," Old Norse amma "grandmother," Middle Irish ammait "old hag," Hebrew em, Arabic umm "mother").

Extended senses include "an old woman, a gossip" (1580s); "a procuress" (1670s); and "any benevolent woman," in American English, where auntie was recorded since c.1790 as "a term often used in accosting elderly women." The French word also has become the word for "aunt" in Dutch, German (Tante), and Danish. Swedish has retained the original Germanic (and Indo-European) custom of distinguishing aunts by separate terms derived from "father's sister" (faster) and "mother's sister" (moster). The Old English equivalents were faðu and modrige. In Latin, too, the formal word for "aunt on mother's side" was matertera. Some languages have a separate term for aunts-in-law as opposed to blood relations.
auntie (n.): 1787, also aunty, familiar diminutive form of aunt. As a form of kindly address to an older woman to whom one is not related, originally in southern U.S., of elderly slave women.
The negro no longer submits with grace to be called "uncle" or "auntie" as of yore. ["Harper's Magazine," October 1883]
aura (n.): 1870 in spiritualism, "subtle emanation around living beings;" earlier "characteristic impression" made by a personality (1859), earlier still "gentle breeze" (late 14c.), from Latin aura "breeze, wind, air," from Greek aura "breath, breeze," from PIE root *awer- (see air (n.1)).
aural (adj.): 1847, "pertaining to the ear," from Latin auris "ear" (see ear (n.1)) + -al (1). Meaning "received or perceived by ear" is attested from 1860. Related: Aurally.
aureate (adj.): early 15c., "gold, gold-colored," also figuratively, "splendid, brilliant," from Latin aureatus "decorated with gold," from aureus "golden," from aurum "gold," from PIE *aus- (cf. Sanskrit ayah "metal," Avestan ayo, Latin aes "brass," Old English ar "brass, copper, bronze," Gothic aiz "bronze," Old Lithuanian ausas "gold"), probably related to root *aus- "to shine" (see aurora).
aureole (n.): early 13c., from Latin aureola (corona), fem. diminutive of aureus "golden" (see aureate). In medieval Christianity, the celestial crown worn by martyrs, virgins, etc., as victors over the flesh.