Merriam-Webster's Collegiate® Dictionary, 11th Edition
QUASH
I. transitive verb
Etymology: Middle English quashen to smash, from Anglo-French quasser, casser, from Latin quassare to shake violently, shatter, frequentative of quatere to shake
Date: 13th century
to suppress or extinguish summarily and completely ,
II. transitive verb
Etymology: Middle English quassen, from Anglo-French casser, quasser to annul, from Late Latin cassare, from Latin cassus void
Date: 14th century
to nullify especially by judicial action