early 15c., "an interjected or exclamatory word," from Middle French interjection (Old French interjeccion, 13c.), from Latin interiectionem (nominative interiectio) "a throwing or placing between," also in grammar and rhetoric, noun of action from past participle stem of intericere "to throw between, set between," from inter "between" (see inter-) + -icere, combining form of iacere "to throw" (from PIE root *ye- "to throw, impel"). Related: Interjectional.
