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].
early 15c., Atlantyke, "of or pertaining to the sea off the west coast of Africa," from Latin Atlanticus, from Greek Atlantikos "of Atlas," adjectival form of Atlas (genitive Atlantos) as used in reference to Mount Atlas in Mauritania (see Atlas). The name has been extended since c. 1600 to the ocean between Europe and Africa, on one side, and the Americas on the other. As a noun late 14c., Athlant, from Old French Atlante.
<a href="https://www.etymonline.com/word/trans-Atlantic">Etymology of trans-Atlantic by etymonline</a>
Harper, D. (n.d.). Etymology of trans-Atlantic. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/trans-Atlantic