"be about to happen" (usually of something unwanted), 1590s, from Latin impendere "to hang over;" figuratively "to be imminent, be near," from assimilated form of in- "into, in, on, upon" (from PIE root *en "in") + pendere "to hang" (from PIE root *(s)pen- "to draw, stretch, spin"). Literal sense in English is by 1780. Related: Impended; impending.
