1625, anslaight, somehow from or on analogy of Du. aanslag "attack," from M.Du. aenslach, from aen "on" + slach "blow," related to slaen "slay." Spelling infl. by obs. (since c.1400) Eng. slaught (n.) "slaughter," from O.E. sleaht (see
slaughter). No record of its use