for definition 1: Old Englidh morð str. neut. and masc. = Old Frisian morth, mord, Old Saxon morð (Middle Low German, Middle Dutch mort, Dutch moora), Old High German mord neut. and masc. (Middle High German mort, German mord), Old Norse morð:—OTeut. *murþosupm, -o-z, cogn. w. Latin mort-, mors death
for definition 2: ? from Old Norse mergð, from margr many
From: Cursor Mundi
Edited by Richard Morris, 1874
Cain slew his brother with the cheek-bone of an ass; he tried to hide the body, but the clay cast it up again.