crass (adj.)

1540s, from Middle French crasse (16c.), from Latin crassus "solid, thick, fat; dense." The literal sense always has been rare in English; meaning "grossly stupid" is recorded from 1650s, from French. Middle English had cras (adj.) "slow, sluggish, tardy" (mid-15c.), also crassitude "thickness." Related: Crassly; crassness.