to put down or suppress completely; quell; subdue: to quash a rebellion.
to make void, annul, or set aside (a law, indictment, decision, etc.).
Origin: 1300–50;Middle Englishquashen to smash, break, overcome, suppress < Old Frenchquasser, in part < Latinquassāre to shake (frequentative of quatere to shake; cf. concussion); in part < Late Latincassāre to annul, derivative of Latincassus empty, void
"to make void, annul, crush," early 14c., from O.Fr. quasser "to break, smash," from L. quassare "to shatter," frequentative of quatere "to shake" (pp. quassus). Meaning "suppress" is from M.L. quassare "make null and void," from L. cassus "empty, void," influenced by quassare.