havoc (n.) Look up havoc at Dictionary.com
early 15c., from Anglo-French havok in phrase crier havok "cry havoc" (late 14c.), a signal to soldiers to seize plunder, from Old French havot "pillaging, looting," related to haver "to seize, grasp," hef "hook," probably from a Germanic source (see hawk (n.)), or from Latin habere "to have, possess." General sense of "devastation" first recorded late 15c.