Ocean
Middle English: from Old French occean, via Latin from Greek ōkeanos ‘great stream encircling the earth's disc’. ‘The ocean’ originally denoted the whole body of water regarded as encompassing the earth's single land mass.
wiktionary
From Middle English *ocean, occean, occian, occyan, from Old French occean (later reborrowed or reinforced by Middle French ocean), from Latin Ōceanus, originally from Ancient Greek Ὠκεανός(Ōkeanós, “Oceanus”, a water deity). Displaced native Old English gārseċġ.
Also commonly referred to as the ocean sea, the sea of ocean (compare Latin mare ōceanum; Old French mer oceane, occeanne mer). Compare Saterland Frisian Oceoan(“ocean”), West Frisian oseaan(“ocean”), Dutch oceaan(“ocean”), German Low German Ozeaan(“ocean”), German Ozean(“ocean”), Danish ocean(“ocean”), Swedish ocean(“ocean”), French océan(“ocean”), Italian oceano(“ocean”).
etymonline
ocean (n.)
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."
