early 14c., rascaile "people of the lowest class, rabble of an army," from Old French rascaille "outcast, rabble" (12c.), perhaps from rasque "mud, filth, scab, dregs," from Vulgar Latin *rasicare "to scrape" (see rash (n.)). The singular form is first attested mid-15c.; extended sense of "low, dishonest person" is from 1580s.