"to wrinkle, make uneven," c. 1600, in rumpled, of uncertain origin, perhaps a variant of rimple "to wrinkle" (c. 1400), from Old English hrympel "wrinkle" (possibly influenced by Middle Dutch rumpelen), related to Old English hrimpan "to fold, wrinkle" (see ramp (v.)). Related: Rumpled; rumpling. As a noun from c. 1500, "a wrinkle, a fold."

Also compare Middle English runkle "become wrinkled" (late 14c.), runkel (n.) "a wrinkle" (early 14c.), probably from Old Norse hrukka.

early 15c., riplen, "to crease, wrinkle;" 1660s, "to present a ruffled surface," of obscure origin, perhaps a frequentative of rip (v.), and compare rip (n.2) and rumple. Transitive sense, in reference to the surface of water, "cause to ripple, agitate lightly," is from 1786. Related: Rippled; rippling.

early 14c.,  cromplen, crumplen, "press into irregular folds, rumple, wrinkle," also intransitive, "contract into wrinkles, shrink, shrivel," frequentative of crumpen "to curl up" (from Old English crump "bent, crooked"), from Proto-Germanic *krumbo- "to press, squeeze, compress" (source also of German krumm "crooked, warped"). Related: Crumpled; crumpling.

1746, "cross-tempered," probably from the frumps (n.) "bad temper" (1660s) and an earlier verb meaning "to mock, browbeat" (1550s), of obscure origin, perhaps imitative of a sneer or derisive snort. See also frump. Sense of "sour-looking, unfashionable" is from 1825, but this may be a shortening of frumple "to wrinkle, crumple" (late 14c.), from Middle Dutch verrompelen "to wrinkle," from ver- "completely" + rompelen "to rumple." Related: Frumpily; frumpiness.