An Etymological Dictionary of the German Language/Annotated/reif
reif, adjective, ‘ripe, mature,’ from the equivalent Middle High German rîfe, Old High German rîfi, adjective; corresponding to the equivalent Old Saxon rîpi, Dutch rijp, Anglo-Saxon rîpe, English ripe; a verbal adjective allied to Anglo-Saxon rī̆pan, ‘to reap’ (whence English to reap), signifying ‘that which can be reaped.’ The Teutonic root rîp, with the original sense ‘to cut, reap’ (compare Anglo-Saxon rîfter, ‘sickle’), has not yet been found in the other Aryan languages.