rejection n.

early 15c., rejecten, "eject, set aside, block from inheritance;" late 15c., "refuse to acquiesce or submit to," from Old French rejecter and directly from Latin reiectus, past participle of reiectare "throw away, cast away, vomit," frequentative of reicere "to throw back," from re- "back" (see re-) + -icere, combining form of iacere "to throw" (from PIE root *ye- "to throw, impel").

The meaning "throw away as undesirable or useless, refuse to take for some purpose" is by 1530s. From 1560s as "to repel or rebuff (someone who makes advances of any kind)," especially of a woman refusing a man as a lover or husband (1580s). The sense of "refuse (something offered)" is by 1660s. The medical sense of "show immune response to a transplanted organ" is from 1953. Related: Rejected; rejecting.

*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."