kill, slay, wound, injure, hurt
戕 centers on violent harm: killing, slaying, wounding, or injuring someone or something.
戕 combines 爿 (a split wood or bed component) with 戈 (a halberd or weapon), suggesting harm or killing with a weapon. The exact historical development is uncertain.
A halberd (戈) beside a split piece of wood (爿) suggests a weapon used to wound or kill.
For ショウ, imagine a warrior showing (ショウ) his halberd before striking: show -> ショウ, and the blade wounds the target.