1560s, of fruits, seeds, etc., "grow ripe, come to maturity," from ripe (adj.) + -en (1). Figurative use by c. 1600. The transitive sense of "bring to maturity, make ripe" also is from 1560s. Related: Ripened; ripening. The earlier verb was simply ripe, Middle English ripen, from late Old English ripian, from the adjective.