Online Etymology Dictionary

occupancy (n.): 1590s, "condition of being an occupant;" from occupant + -cy. Meaning "fact of occupying" is from 1833; that of "proportion of available space that is occupied" is attested by 1974.
occupant (n.): 1590s, "one who takes possession of something having no owner," from Middle French occupant (15c.) or directly from Latin occupantem (nominative occupans), present participle of occupare "to take possession of" (see occupy). Earlier noun form was ocupier (early 14c.).
occupation (n.): early 14c., "fact of holding or possessing;" mid-14c., "a being employed in something," also "a particular action," from Old French occupacion "pursuit, work, employment; occupancy, occupation" (12c.), from Latin occupationem (nominative occupatio) "a taking possession; business, employment," noun of action from past participle stem of occupare (see occupy). Meaning "employment, business in which one engages" is late 14c. That of "condition of being held and ruled by troops of another country" is from 1940.
occupational (adj.): 1850, from occupation + -al (1). Occupational therapy is attested by 1918; occupational risk by 1951. Related: Occupationally.
occupied (adj.): late 15c., past participle adjective from occupy (v.). Of countries overrun by others, from 1940, originally with reference to France.
occupier (n.): late 14c., agent noun from occupy.
occupy (v.): mid-14c., "to take possession of," also "to take up space or time, employ (someone)," irregularly borrowed from Old French occuper "occupy (a person or place), hold, seize" (13c.) or directly from Latin occupare "take over, seize, take into possession, possess, occupy," from ob "over" (see ob-) + intensive form of capere "to grasp, seize" (see capable). The final syllable of the English word is difficult to explain, but it is as old as the record; perhaps from a modification made in Anglo-French. During 16c.-17c. a common euphemism for "have sexual intercourse with" (sense attested from early 15c.), which caused it to fall from polite usage.
"A captaine? Gods light these villaines wil make the word as odious as the word occupy, which was an excellent good worde before it was il sorted." [Doll Tearsheet in "2 Henry IV"]
Related: Occupied; occupying.
occur (v.): 1520s, "meet, meet in argument," from Middle French occurrer "happen unexpectedly" or directly from Latin occurrere "run to meet, run against, befall, present itself," from ob "against, toward" (see ob-) + currere "to run" (see current (adj.)). Sense development is from "meet" to "present itself" to "appear" to "happen" ("present itself in the course of events"). Meaning "to come into one's mind" is from 1620s. Related: Occurred; occurring.
occurrence (n.): 1530s, from Middle French occurrence "unexpected happening" or directly from Medieval Latin occurrentia, from Latin occurentem (nominative occurens), present participle of occurrere (see occur).
ocean (n.): late 13c., from Old French occean "ocean" (12c., Modern French océan), from Latin oceanus, from Greek okeanos, the great river or sea surrounding the disk of the Earth (as opposed to the Mediterranean), of unknown origin. Personified as Oceanus, son of Uranus and Gaia and husband of Tethys. In early times, when the only known land masses were Eurasia and Africa, the ocean was an endless river that flowed around them. Until c. 1650, commonly ocean sea, translating Latin mare oceanum. Application to individual bodies of water began 14c.; there are usually reckoned to be five of them, but this is arbitrary; also occasionally applied to smaller subdivisions, such as German Ocean "North Sea."
Oceania: "southern Pacific island and Australia, conceived as a continent," 1849, Modern Latin, from French Océanie (c. 1812). Apparently coined by Danish geographer Conrad Malte-Brun (1755-1826). Earlier in English as Oceanica (1832). Oceania was the name of one of the superstates in Orwell's "Nineteen Eighty-Four." Oceanea, name of James Harrington's 17c. ideal state, later was applied to the British empire.
oceanic (adj.): 1650s, probably from French océanique, from océan (see ocean).
oceanographer (n.): 1886, agent noun from oceanography.
oceanography (n.): 1859, coined in English from ocean + -graphy; on analogy of geography. French océanographie is attested from 1580s but is said to have been rare before 1876. Related: Oceanographic.
ocelot (n.): "large wildcat of Central and South America," 1775, from French ocelot, a word formed by French naturalist Georges-Louis Leclerc, Comte de Buffon (1707-1788), from Nahuatl (Aztecan) ocelotl "jaguar" (in full tlalocelotl, a compound formed with tlalli "field").
ocher: see ochre.
ochlocracy (n.): "government by the rabble," 1580s, from French ochlocratie (1560s), from Greek okhlokratia (Polybius) "mob rule," the lowest grade of democracy, from kratos "rule, power, strength" (see -cracy) + okhlos "mob, populace," perhaps literally "moving mass," from PIE *wogh-lo-, from root *wegh- "to go, transport" in a vehicle (see weigh). For sense development, compare mob (n.). Related: Ochlocratic; ochlocratical. Greek also had okhlagogos "mob-leader, ochlagogue."
ochre (n.): type of clayey soil (much used in pigments), late 14c., from Old French ocre (c. 1300) and directly from Late Latin ocra, from Latin ochra, from Greek ochra, from ochros "pale yellow," of unknown origin. As a color name, "brownish-yellow," it is attested from mid-15c. Related: Ochreous.
octa-: before vowels oct-, word-forming element meaning "eight," from Greek okta-, okt-, from PIE *okto(u) "eight" (see eight). The variant form octo- often appears in words taken from Latin, but the Greek form is said to be the more common in English.
octagon (n.): 1650s, from Latin octagonos, from Greek oktagononos, literally "eight-angled," from okta- comb. form of okto "eight" (see eight) + gonia "angle," related to gony "knee" (see -gon). Also octogon (1650s), from French octogone.
octagonal (adj.): 1570s, from octagon + -al (1).
octahedron (n.): 1560s, from Greek oktahedron, neuter of oktahedros "eight-sided," from okta- "eight" (see octa-) + hedra "seat" (see sedentary). Related: Octahedral.
octane (n.): hydrocarbon of the methane series, 1872, coined from octo- (see octa-) + -ane; so called because it has eight carbon atoms. A fuel's octane rating, in reference to its anti-knocking quality, is attested from 1932.
octant (n.): instrument for making angular measurements in navigation or astronomy, 1731, from Late Latin octans "the eighth part," from octo "eight" (see octa-) on analogy of quadrant. In geometry, octant meant "the eighth part of a circle."
octave (n.): c. 1300, utaves (plural, via Anglo-French from popular Old French form oitieve, otaves), reformed in early 15c., from Medieval Latin octava, from Latin octava dies "eighth day," fem. of octavus "eighth," from octo (see eight). Originally "period of eight days after a festival," also "eighth day after a festival" (counting both days, by inclusive reckoning, thus if the festival was on a Sunday, the octaves would be the following Sunday). Verse sense of "stanza of eight lines" is from 1580s; musical sense of "note eight diatonic degrees above (or below) a given note" is first recorded 1650s, from Latin octava (pars) "eighth part." Formerly English eighth was used in this sense (mid-15c.)
Octavia: fem. proper name, from Latin, fem. of Octavius, literally "the eighth" (see Octavian).
Octavian: masc. proper name, from Latin, from Octavius, from octavus "eighth," from octo (see eight).
But although we find so marked differences in the use of the numerals as names, it is impossible to believe that this use did not arise in the same way for all; that is, that they were at first used to distinguish children by the order of birth. But when we find them as praenomina in historical times it is evident that they no longer referred to order of birth. [George Davis Chase, "The Origin of Roman Praenomina," "Harvard Studies in Classical Philology," 1897]
octavo (n.): 1580s, printer's word for sheets folded to make eight leaves, from Latin in octavo "in the eighth," ablative of octavus "eighth" (see octave). Abbreviation is 8vo.
octo-: word-forming element, before vowels oct-, from comb. form of Latin octo "eight" (see octa-).
October: c. 1050, from Latin October (mensis), from octo "eight," from PIE root *octo(u)- "eight" (see eight). Eighth month of the old Roman calendar (pre-46 B.C.E.), which began the year in March. For -ber see December. Replaced Old English winterfylleð. In Russian history, October Revolution (in which the Bolsheviks overthrew the Provisional Government) happened Nov. 7, but because Russia had not at that time adpoted the Gregorian calendar reform, this date was reckoned there (Old Style) as Oct. 25.
Octobrist (n.): 1., from Russian oktyabrist, "member of the league formed October 1905 in response to imperial policies"; 2., from Russian Oktyabryonok, "member of a Russian communist children's organization founded 1925 and named in honor of the October Revolution."
octogenarian (n.): 1789, with -an + French octogénaire "aged 80," from Latin octogenarius "containing eighty," from octogeni "eighty each," related to octoginta "eighty," from octo "eight" (see eight) + -genaria "ten times," from PIE *dkm-ta-, from *dekm- "ten" (see ten). As an adjective from 1784.
octopod: 1826 (adj.); 1835 (n.), from Latinized form of Greek oktopod-, from stem of oktopous (see octopus).
octopus (n.): 1758, genus name of a type of eight-armed cephalopod mollusks, from Greek oktopous, literally "eight-foot," from okto "eight" (see eight) + pous "foot," from PIE root *ped- (1) "a foot" (see foot (n.)). Proper plural is octopodes, though octopuses probably works better in English. Octopi (1817) is from mistaken assumption that -us in this word is the Latin noun ending that takes -i in plural.
octoroon (n.): 1861, irregular formation from Latin octo "eight" (see eight) + suffix abstracted from quadroon (in which the suffix actually is -oon). Offspring of a quadroon and a white; so called for having one-eighth Negro blood.
octuple (adj.): "eightfold," c. 1600, from Latin octuplus "eightfgold," from octo "eight" (see octo-) + -plus "-fold" (see plus).
ocular (adj.): c. 1500, from Late Latin ocularis "of the eyes," from Latin oculus "an eye," from PIE root *okw- "to see" (source also of Gothic augo, Old English eage "eye;" see eye (n.)). As a noun, 1835, from the adjective.
oculist (n.): "eye doctor," 1610s, from French oculiste (16c.), from Latin oculus "an eye" (see eye (n.)).
oculus: "an eye," plural oculi, 1857, from Latin oculus "an eye" (see eye (n.)).
oda (n.): room in a harem, 1620s, from Turkish odah "hall, chamber."
odalisque (n.): "female slave in a harem," 1680s, from French odalisque (1660s), from Turkish odaliq "maidservant," from odah "room in a harem," literally "chamber, hall," + -liq, suffix expressing function. In French, the suffix was confused with Greek -isk(os) "of the nature of, belonging to."
odd (adj.): c. 1300, "constituting a unit in excess of an even number," from Old Norse oddi "third or additional number," as in odda-maðr "third man, odd man (who gives the casting vote)," odda-tala "odd number." The literal meaning of Old Norse oddi is "point of land, angle" (related via notion of "triangle" to oddr "point of a weapon"); from Proto-Germanic *uzdaz "pointed upward" (source also of Old English ord "point of a weapon, spear, source, beginning," Old Frisian ord "point, place," Dutch oord "place, region," Old High German ort "point, angle," German Ort "place"), from PIE *uzdho- (source also of Lithuanian us-nis "thistle"). None of the other languages, however, shows the Old Norse development from "point" to "third number." Used from late 14c. to indicate a surplus over any given sum.

Sense of "strange, peculiar" first attested 1580s from notion of "odd one out, unpaired one of three" (attested earlier, c. 1400, as "singular" in a positive sense of "renowned, rare, choice"). Odd job (c. 1770) is so called from notion of "not regular." Odd lot "incomplete or random set" is from 1897. The international order of Odd Fellows began as local social clubs in England, late 18c., with Masonic-type trappings; formally organized 1813 in Manchester.
oddball (n.): "eccentric or unconventional person," 1948, from odd + ball (n.1). Earlier (1946) as an adjective, used by aviators.
odditorium (n.): 1914, from oddity + -orium (see -ory).
oddity (n.): 1713, "odd characteristic or trait," a hybrid from odd + -ity. Meaning "odd person" is first recorded 1748.
oddly (adv.): c. 1300, from odd + -ly (2).
oddments (n.): 1780, a hybrid with a Latin suffix on a Germanic word, from odd (q.v.), on model of fragments. Related: Oddment.
oddness (n.): late 14c., from odd + -ness.
odds (n.): in wagering sense, found first in Shakespeare ("2 Henry IV," 1597), probably from earlier sense of "amount by which one thing exceeds or falls short of another" (1540s), from odd (q.v.), though the sense evolution is uncertain. Until 19c. treated as a singular, though obviously a plural (compare news).
ode (n.): 1580s, from Middle French ode (c. 1500), from Late Latin ode "lyric song," from Greek oide, Attic contraction of aoide "song, ode;" related to aeidein (Attic aidein) "to sing;" aoidos (Attic oidos) "a singer, singing;" aude "voice, tone, sound," probably from a PIE *e-weid-, perhaps from root *wed- "to speak." In classical use, "a poem intended to be sung;" in modern use usually a rhymed lyric, often an address, usually dignified, rarely extending to 150 lines. Related: Odic.