early 15c., "intercession, intercessory prayer," from Middle French intervention or directly from Late Latin interventionem (nominative interventio) "an interposing, a giving security," literally "a coming between," noun of action from past participle stem of Latin intervenire "to come between, interrupt," from inter "between" (see inter-) + venire "to come," from a suffixed form of PIE root *gwa- "to go, come." Later "act of intervening" in any way; in 19c.-20c. often of international relations; by 1983 of interpersonal intrusions by friends or family meant to reform a life felt to be going wrong.
