1827, "situated across the ocean," from trans- + oceanic. Meaning "passing over the sea" is recorded from 1868.
Entries linking to trans-oceanic
trans-
word-forming element meaning "across, beyond, through, on the other side of, to go beyond," from Latin trans (prep.) "across, over, beyond," perhaps originally present participle of a verb *trare-, meaning "to cross," from PIE *tra-, variant of root *tere- (2) "cross over, pass through, overcome." In chemical use indicating "a compound in which two characteristic groups are situated on opposite sides of an axis of a molecule" [Flood].
oceanic adj.
"belonging or relating to the ocean," 1650s, probably from French océanique, from océan (see ocean).