invasion (n.)youdaoicibaDictYouDict[invasion 词源字典]
mid-15c., from Old French invasion "invasion, attack, assaut" (12c.), from Late Latin invasionem (nominative invasio) "an attack, invasion," noun of action from past participle stem of Latin invadere "go into, fall upon, attack, invade," from in- "in" (see in- (2)) + vadere "go, walk" (see vamoose).[invasion etymology, invasion origin, 英语词源]