havoc: [15] The ancestry of havoc is a mystery, but it seems originally to have been an exclamation, probably Germanic, used as a signal to begin plundering. This was adopted into Old French as havot, which was used in the phrase crier havot ‘shout ‘havot’,’ hence ‘let loose destruction and plunder’. Havot became altered in Anglo-Norman to havok, the form in which English adopted it; and in due course cry havoc gave rise to the independent use of havoc as ‘destruction, devastation’. [havoc etymology, havoc origin, 英语词源]