1640s, "to unfold, open out, expand," from Latin evolvere "to unroll, roll out, roll forth, unfold," especially of books; figuratively "to make clear, disclose; to produce, develop," from assimilated form of ex "out" (see ex-) + volvere "to roll," from PIE root *wel- (3) "to turn, revolve." Meaning "to develop by natural processes to a higher state" is from 1832. Related: Evolved; evolving.