Is it ensure, insure, or assure?
Old English ripe "ready for reaping, fit for eating, mature," from West Germanic *ripijaz (cf. Old Saxon ripi, Middle Dutch ripe, Dutch rijp, Old High German rifi, German reif); related to Old English repan "to reap" (see reap). Meaning "ready for some action or effect" is from 1590s. Related: Ripely; ripeness.