slaught (n.)

c. 1300, "the killing of a person, murder; the killing of large numbers of persons in battle;" mid-14c., "the killing of cattle or sheep or other animals for food;" from a Scandinavian source akin to Old Norse slatr "a butchering, butcher meat," slatra "to slaughter," slattr "a mowing," related to Old Norse sla "to strike," from Proto-Germanic *slagan- (see slay (v.)).

The form was perhaps influenced by obsolete slaught "killing, manslaughter, carnage; butchery of animals," the native cognate, which is from Old English sliht, sleht, slieht "stroke, slaughter, murder, death; animals for slaughter;" as in sliehtswyn "pig for killing." The Elizabethans had an adjective slaughterous.