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