Meaning

noun an abrupt emphatic exclamation expressing emotion

noun the action of interjecting or interposing an action or remark that interrupts

originFrom Middle English interjeccioun, from Old French interjection (13th century), from Latin interiectiōnem, accusative singular of interiectiō (“throwing or placing between; interjection”), perfect passive participle of intericiō (“throw or place between”), from inter (“between”) + iaciō (“throw”). Displaced Old English betwēoxāworpennes (literally “between-thrown-out-ness”), a calque of the Latin.

Etymology from Wiktionary, CC BY-SA 3.0