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].
"bridge," in anatomy and in various Latin expressions, from Latin pons "bridge, connecting gallery, walkway," earlier probably "way, passage," from PIE root *pent- "to go, tread" (see find (v.)). Especially pons asinorum "bridge of asses," nickname since early 16c. for the fifth proposition of the first book of Euclid, which students and slow wits find difficulty in "getting over": if two sides of a triangle are equal, the angles opposite these sides also are equal. "The original allusion seems to have been to the difficulty of getting asses to cross a bridge" [Century Dictionary]. The Latin word is the source of Italian ponte, French pont, Spanish puente.
<a href="https://www.etymonline.com/word/transpontine">Etymology of transpontine by etymonline</a>
Harper, D. (n.d.). Etymology of transpontine. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/transpontine