1540s, perhaps an alteration of drysning "a falling of dew" (c.1400), from Old English -drysnian, related to dreosan "to fall," from PIE root *dhreu- (see drip, v.). Or perhaps a frequentative of Middle English dresen "to fall," from Old English dreosan. Related: Drizzled; drizzling. As a noun, from 1550s.