1520s, "meet, meet in argument," from 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" (from PIE root *kers- "to run"). 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.

"that which presents itself, that which happens without design or expectation," 1530s, from French occurrence "unexpected happening" or directly from Medieval Latin occurrentia, from Latin occurentem (nominative occurens), present participle of occurrere (see occur). The adjective occurrent "occurring, happening, incidental" (mid-15c.) is long obsolete.

c. 1300, occean, "the vast body of water on the surface of the globe," from Old French occean "ocean" (12c., Modern French océan), from Latin oceanus, from Greek ōkeanos, the great river or sea surrounding the disk of the Earth (as opposed to the Mediterranean), a word of unknown origin; Beekes suggests it is Pre-Greek. 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. (occean Atlantyke, 1387); five of them are usually reckoned, but this is arbitrary. The English word also occasionally was applied to smaller subdivisions, such as German Ocean "North Sea."

"the southern Pacific islands 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 was the name of James Harrington's 17c. ideal state, and the name later was applied to the British empire. Related: Oceanean.

"belonging or relating to the ocean," 1650s, probably from French océanique, from océan (see ocean).

"a student of the seas, one who systematically studies the ocean," 1886, agent noun from oceanography.

"the science of the oceans," 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.

"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 "(orderless) crowd, multitude, throng; disturbance, annoyance," which is probably literally "moving mass," from PIE *wogh-lo-, suffixed form of root *wegh- "to go, move."  "Several possibilities exist for the semantic development: e.g. an agent noun *'driving, carrying, moving', or an instrument noun *'driver, carrier, mover'. ... An original meaning 'drive' could easily develop into both 'stirred mass, mob' and 'spiritual excitement, unrest'" [Beekes]. For sense development, compare mob (n.). Related: Ochlocrat, ochlocratic; ochlocratical. Greek also had okhlagogos "mob-leader, ochlagogue."