interjection n.

word-forming element used freely in English, "between, among, during," from Latin inter (prep., adv.) "among, between, betwixt, in the midst of" (also used extensively as a prefix), from PIE *enter "between, among" (source also of Sanskrit antar, Old Persian antar "among, between," Greek entera (plural) "intestines," Old Irish eter, Old Welsh ithr "among, between," Gothic undar, Old English under "under"), a comparative of root *en "in."

A living prefix in English from 15c. and used with Germanic as well as Latinate words. Spelled entre- in French; most words borrowed into English in that form were re-spelled 16c. to conform with Latin except entertain, enterprise. In Latin, spelling shifted to intel- before -l-, hence intelligence, etc.

*yē-, Proto-Indo-European root meaning "to throw, impel."

It forms all or part of: abject; abjection; adjacence; adjacent; adjective; aphetic; catheter; circumjacent; conjecture; deject; ease; ejaculate; eject; enema; gist; ictus; interjacent; inject; interject; interjection; jess; jet (v.1) "to sprout or spurt forth, shoot out;" jet (n.1) "stream of water;" jete; jetsam; jettison; jetton; jetty (n.) "pier;" joist; jut; object; objection; objective; paresis; project; projectile; reject; rejection; subjacent; subject; subjective; trajectory.

It is the hypothetical source of/evidence for its existence is provided by: Hittite ijami "I make;" Latin iacere "to throw, cast."