name for the sea that anciently lay between Eurasia and Africa-Arabia, coined 1893 by German geologist Eduard Suess, from Tethys, name of a Greek sea goddess, sister and consort of Oceanus.
"of or pertaining to the Greek sea-god Proteus," 1590s, from Greek Prōteus, son of Oceanus and Tethys, who could change his form at will; hence, "readily assuming different shapes, exceedingly variable." His name is literally "first," from prōtos "first" (see proto-).
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."