An Etymological Dictionary of the German Language/Annotated/Schlacht
Schlacht, feminine, ‘battle, engagement,’ from Middle High German slahte, slaht, feminine, ‘killing, slaughter, battle,’ Old High German slahta, feminine, Old Saxon man-slahta, feminine, ‘death-blow, killing’; an abstract formed by the sem. suffix -tâ- (as in Schande), from the Teutonic root slah, ‘to slay.’ For Schlacht in the sense of ‘sort’ see Geschlecht. Schlacht, ‘dyke, embankment,’ is also a derivative of schlagen, ‘to make firm by beating,’ which sense Middle High German slahen may have even in the classical poets. —