Etymology
From Middle English runkel (“wrinkle, crease”). Cognate with Scots runkil (“wrinkle, crease”). Of uncertain origin, perhaps from a diminutive ( + -le) of Old Norse *hrunka, hrukka (“wrinkle”), from Proto-Germanic *hrunkwǭ (“wrinkle”). The verb is from Middle English runklen (“to wrinkle”), from the noun. Compare also Old Swedish rynkia (whence Swedish rynka (“to wrinkle”)).