Havoc
late Middle English: from Anglo-Norman French havok, alteration of Old French havot, of unknown origin. The word was originally used in the phrase cry havoc (Old French crier havot ) ‘to give an army the order havoc’, which was the signal for plundering.
wiktionary
From Middle English havok, havyk, from Old French havok in the phrase crier havok(“ cry havoc”) a signal to soldiers to seize plunder, from Old French crier(“cry out, shout”) + havot(“pillaging, looting”).
etymonline
havoc (n.)
early 15c., from the expression cry havoc "give the signal to pillage" (Anglo-French crier havok, late 14c.). Havok, the signal to soldiers to seize plunder, is from Old French havot "pillaging, looting" (in crier havot), which is 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.
