Oceanus
noun
Oce·anus ō-ˈsē-ə-nəs 
: a Titan who rules over a great river encircling the earth in Greek mythology
Word History
Etymology
Latin Ōceanus, borrowed from Greek Ōkeanós, personification of Ōkeanós "the sea flowing around the land mass of the known world" — more at ocean
First Known Use
1567, in the meaning defined above