Online Etymology Dictionary

objet (n.): "an object on display, an ornament," 1857, from French objet (14c.), especially in objet d'art (1865), from Latin objectus (see object (n.)).
objurgate (v.): 1610s, from Latin obiurgatus, past participle of obiurgare "to chide, rebuke," from ob- (see ob-) + iurgare "to quarrel, scold," from phrase iure agere "to deal in a lawsuit," from ablative of ius "right; law; suit" (see just (adj.)) + agere "to do, act, set in motion" (see act (n.)). Related: Objurgatory.
objurgation (n.): 1540s, from Latin obiurgationem (nominative obiurgatio) "a chiding, reproving, reproof," noun of action from past participle stem of obiurgare (see objurgate).
oblate (adj.): "flattened on the ends," 1705, from Medieval Latin oblatus "flattened," from Latin ob "toward" (see ob-) + latus, abstracted from its opposite, prolatus "lengthened" (see oblate (n.)).
oblate (n.): "person devoted to religious work," 1756, from Medieval Latin oblatus, noun use of Latin oblatus, variant past participle of offerre "to offer, to bring before," from ob- (see ob-) + latus "carried, borne" (used as suppletive past participle of ferre "to bear"), said by Watkins to be from *tlatos, from PIE root *tele- "to bear, carry" (see extol), but de Vaan says "No good etymology available."
oblation (n.): early 15c., from Old French oblacion "offering, pious donation" and directly from Latin oblationem (nominative oblatio) "an offering, presenting, gift," in Late Latin "sacrifice," from Latin oblatus (see oblate (n.)).
obligate (v.): 1540s, "to bind, connect;" 1660s, "to put under moral obligation," back-formation from obligation, or else from Latin obligatus, past participle of obligare (see oblige). Oblige, with which it has been confused since late 17c., means "to do one a favor." Related: Obligated; obligating.
obligation (n.): c. 1300, from Old French obligacion "obligation, duty, responsibility" (early 13c.) and directly from Latin obligationem (nominative obligatio) "an engaging or pledging," literally "a binding" (but rarely used in this sense), noun of action from past participle stem of obligare (see oblige). The notion is of binding with promises or by law or duty.
obligatory (adj.): c. 1400, from Old French obligatoire "creating an obligation, obligatory," and directly from Late Latin obligatorius "binding," from obligat-, past participle stem of obligare (see oblige).
oblige (v.): c. 1300, "to bind by oath," from Old French obligier "engage one's faith, commit (oneself), pledge" (13c.), from Latin obligare "to bind, bind up, bandage," figuratively "put under obligation," from ob "to" (see ob-) + ligare "to bind," from PIE root *leig- "to bind" (see ligament). Main modern meaning "to make (someone) indebted by conferring a benefit or kindness" is from 1560s. Related: obliged; obliging.
obliged (adj.): c. 1600, past participle adjective from oblige. To be obliged "be bound by ties of gratitude" is from 1540s.
obligee (n.): "person to whom another is bound by contract," 1570s, from oblige + -ee.
obliging (adj.): "willing to do service or favors," 1630s, present participle adjective from oblige. Related: Obligingly.
obligor (n.): "person who binds himself to another by contract," 1540s, agent noun in Latin form from oblige.
oblique (adj.): early 15c., from Middle French oblique (14c.) and directly from Latin obliquus "slanting, sidelong, indirect," from ob "against" (see ob-) + root of licinus "bent upward," from PIE root *lei- "to bend, be movable" (see limb (n.1)). As a type of muscles, in reference to the axis of the body, 1610s (adj.), 1800 (n.). Related: Obliquely; obliqueness.
obliquity (n.): early 15c., from Middle French obliquité (14c.), from Latin obliquitatem (nominative obliquitas) "slanting direction, obliquity," noun of quality from obliquus (see oblique).
obliterate (v.): c. 1600, from Latin obliteratus, past participle of obliterare "cause to disappear, blot out, erase, efface," figuratively "cause to be forgotten," from ob "against" (see ob-) + littera (also litera) "letter, script" (see letter (n.)); abstracted from phrase literas scribere "write across letters, strike out letters." Related: Obliterated; obliterating.
obliteration (n.): 1650s, from Late Latin obliterationem (nominative obliteratio), noun of action from past participle stem of obliterare (see obliterate).
obliviate (v.): 1660s, from Latin oblivium (see oblivion). Related: Obliviated; obliviating.
oblivion (n.): late 14c., "state or fact of forgetting," from Old French oblivion (13c.) and directly from Latin oblivionem (nominative oblivio) "forgetfulness; a being forgotten," from oblivisci (past participle oblitus) "forget," originally "even out, smooth over, efface," from ob "over" (see ob-) + root of levis "smooth," from PIE *lei-w-, from root *(s)lei- "slime, slimy, sticky" (see slime (n.)). Meaning "state of being forgotten" is early 15c.
oblivious (adj.): mid-15c., from Latin obliviosus "forgetful, that easily forgets; producing forgetfulness," from oblivion (see oblivion). Meaning "unaware, unconscious (of something)" is from 1862, formerly regarded as erroneous, this is now the general meaning and the word has lost its original sense of "no longer aware or mindful." Properly should be used with to, not of. Related: Obliviously; obliviousness.
oblong (adj.): early 15c., from Latin oblongus "more long than broad," originally "somewhat long," from ob "to, toward," here perhaps intensive (see ob-) + longus "long" (see long (adj.)). As a noun from c. 1600.
obloquy (n.): mid-15c., "evil speaking," from Late Latin obloquium "speaking against, contradiction," from Latin obloqui "to speak against, contradict," from ob "against" (see ob-) + loqui "to speak," from PIE *tolk(w)- "to speak" (see locution). Related: Obloquious.
obnoxious (adj.): 1580s, "subject to the authority of another," from Latin obnoxiosus "hurtful, injurious," from obnoxius "subject, exposed to harm," from ob "to, toward" (see ob-) + noxa "injury, hurt, damage entailing liability" (see noxious). Meaning "subject to something harmful" is 1590s; meaning "offensive, hateful" is first recorded 1670s, influenced by noxious.
Obnoxious has two very different senses, one of which (exposed or open or liable to attack or injury) requires notice because its currency is now so restricted that it is puzzling to the uninstructed. It is the word's rightful or de jure meaning, and we may hope that scholarly writers will keep it alive. [Fowler]
Related: Obnoxiously; obnoxiousness.
obnubilate (v.): 1580s, from Latin obnibulatus, past participle of obnubilare "to cover with clouds or fog," from ob- (see ob-) + verb from Latin nubes "cloud" (see nuance). Related: Obnubilated; obnubilating; obnubilation.
obo: also o.b.o., abbreviation of or best offer, by 1969.
oboe (n.): 1724, from Italian oboe, from phonetic spelling of Middle French hautbois (itself borrowed in English 16c. as hautboy), from haut "high, loud, high-pitched" (see haught) + bois "wood" (see bush (n.)). So called because it had the highest register among woodwind instruments. Related: Oboist.
obol (n.): ancient Greek small coin and weight, 1660s, from Latin obolus, from Greek obolos, identical with obelos "a spit, needle." From the original shape.
obscene (adj.): 1590s, "offensive to the senses, or to taste and refinement," from Middle French obscène (16c.), from Latin obscenus "offensive," especially to modesty, originally "boding ill, inauspicious," of unknown origin; perhaps from ob "onto" (see ob-) + caenum "filth." Meaning "offensive to modesty or decency" is attested from 1590s. Legally, in U.S., it hinged on "whether to the average person, applying contemporary community standards, the dominant theme of the material taken as a whole appeals to a prurient interest." [Justice William Brennan, "Roth v. United States," June 24, 1957]; refined in 1973 by "Miller v. California":
The basic guidelines for the trier of fact must be: (a) whether 'the average person, applying contemporary community standards' would find that the work, taken as a whole, appeals to the prurient interest, (b) whether the work depicts or describes, in a patently offensive way, sexual conduct specifically defined by the applicable state law; and (c) whether the work, taken as a whole, lacks serious literary, artistic, political, or scientific value.
Related: Obscenely.
obscenity (n.): 1580s, "obscene quality," from French obscénité, from Latin obscenitatem (nominative obscenitas) "inauspiciousness, filthiness," from obscenus "offensive" (see obscene). Meaning "a foul or loathsome act" is 1610s. Sense of "an obscene utterance or word" is attested by 1690. Related: Obscenities.
obscurant (adj.): 1878, from Latin obscurantem (nominative obscurans), present participle of obscurare (see obscure (v.)).
obscurantism (n.): "opposition to enlightenment," 1834, from German obscurantismus (18c.); see obscurant + -ism.
obscurantist (n.): 1841; see obscurantism + -ist.
obscuration (n.): late 15c., from Latin obscurationem (nominative obscuratio) "a darkening, obscuring," noun of action from past participle stem of obscurare (see obscure (v.)).
obscure (adj.): c. 1400, "dark," figuratively "morally unenlightened; gloomy," from Old French obscur, oscur "dark, clouded, gloomy; dim, not clear" (12c.) and directly from Latin obscurus "dark, dusky, shady," figuratively "unknown; unintelligible; hard to discern; from insignificant ancestors," from ob "over" (see ob-) + -scurus "covered," from PIE *(s)keu- "to cover, conceal" (see sky). Related: Obscurely.
obscure (v.): early 15c., "to cover (something), cloud over," from obscure (adj.) or else from Middle French obscurer, from Latin obscurare "to make dark, darken, obscure," from obscurus. Related: Obscured; obscuring.
obscurity (n.): late 15c., "absence of light;" 1610s with meaning "condition of being unknown;" from obscure (adj.) + -ity; or else from Middle French obscurité, variant of Old French oscureté "darkness, gloom; vagueness, confusion; insignificance" (14c.), from Latin obscuritatem (nominative obscuritas) "darkness, indistinctness, uncertainty," from obscurus.
obsecration (n.): late 14c., from Latin obsecrationem (nominative obsecratio) "a beseeching, imploring, supplication, entreaty," noun of action from past participle stem of obsecrare "to beseech, entreat" (on religious grounds), from ob- (see ob-) + sacrare "to make or declare sacred" (see sacred).
obsequies (n.): "funeral rites," plural of obsequy.
obsequious (adj.): late 15c., "prompt to serve," from Middle French obséquieux (15c.), from Latin obsequiosus "compliant, obedient," from obsequium "compliance, dutiful service," from obsequi "to accommodate oneself to the will of another," from ob "after" (see ob-) + sequi "to follow" (see sequel). Pejorative sense of "fawning, sycophantic" had emerged by 1590s. Related: Obsequiously; obsequiousness (mid-15c.).
obsequy (n.): late 14c., from Old French obseque, osseque "funeral rites," from Medieval Latin obsequiae, influenced in sense by confusion of Latin obsequium "compliance" (see obsequious) with exsequiae "funeral rites." Now usually in plural, obsequies.
observable (adj.): c. 1600, from Latin observabilis "remarkable, observable," from observare (see observe). Related: Observably; observability.
observance (n.): early 13c., "act performed in accordance with prescribed usage," especially a religious or ceremonial one, from Old French observance, osservance "observance, discipline," or directly from Latin observantia "act of keeping customs, attention, respect, regard, reverence," from observantem (nominative observans), present participle of observare (see observe). Observance is the attending to and carrying out of a duty or rule. Observation is watching, noticing.
observant (adj.): 1590s, from observe + -ant, or else from French observant, past participle of observer (see observance). In reference to Judaism, from 1902. As a noun from late 15c. Related: Observantly; observantness.
observation (n.): late 14c., "performance of a religious rite," from Latin observationem (nominative observatio) "a watching over, observance, investigation," noun of action from past participle stem of observare (see observe). Sense of "act or fact of paying attention" is from 1550s. Meaning "a remark in reference to something observed" first recorded 1590s.
observative (adj.): 1610s, from Latin observat-, past participle stem of observare (see observe) + -ive.
observatory (n.): "building for observing astronomical phenomena," 1670s (in reference to Greenwich), from French observatoire, from observer (v.); see observe.
observe (v.): late 14c., "to hold to" (a manner of life or course of conduct), from Old French observer, osserver "to observe, watch over, follow" (10c.), from Latin observare "watch over, note, heed, look to, attend to, guard, regard, comply with," from ob "over" (see ob-) + servare "to watch, keep safe," from PIE root *ser- (1) "to protect." Meaning "to attend to in practice, to keep, follow" is attested from late 14c. Sense of "watch, perceive, notice" is 1560s, via notion of "see and note omens." Meaning "to say by way of remark" is from c. 1600. Related: Observed; observing.
observer (n.): 1550s, "one who keeps a rule, custom, etc.," agent noun from observe. Meaning "one who watches and takes notice" is from 1580s; this is the sense of the word in many newspaper names.
obsess (v.): c. 1500, "to besiege," from Latin obsessus, past participle of obsidere "watch closely; besiege, occupy; stay, remain, abide" literally "sit opposite to," from ob "against" (see ob-) + sedere "sit" (see sedentary). Of evil spirits, "to haunt," from 1530s. Psychological sense is 20c. Related: Obsessed; obsessing.