ripen

From Middle English *ripenen, extended form of ripen, from Old English rīpian. In the modern form, equivalent to ripe + -en (inchoative and factitive suffix). As in several other verbs, the alteration seems to have occurred during the time when the infinitive and plural ending -en was in the process of being lost (and was thus open to reinterpretation). The earliest attestation is deverbal Middle English ripening (“causing ripeness, ripening”).