E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
No quarter. In a tract entitled The Office of the Constable and Mareschall in the Tyme of Werre
(contained in the Black Book of the Admiralty), one of the chapters is, The peyne of hym that crieth havock, and of them that followeth himItem si quis inventus fuerit qui clamorem inceperit qui vocatur havok.