In the oracle bone script, it was an ideogrammic compound (會意): 戈(“spear”) + [Term?] (“hair”) – a man impaled in the head.
In the bronze script, 人 (“man”) was added under the hair to accentuate the killing of the man. In some bronze inscriptions, 殳 (“spear”) or 攴 was used in place of 戈.
In the bamboo and silk script, symbol representing the man being killed corrupted into 杀: 乂(“weapon for killing”) + 𣎳. The seal script inherits this: Phono-semantic compound (形聲, OC *sreːds, *sreːd): phonetic 𣏂 + semantic 殳(“spear”).