strong
毅 centers on inner strength and resolute determination: being strong-willed, firm, and unyielding in purpose.
毅 combines 豙 (a boar or pig) with 殳 (a weapon or action), suggesting the fierce, unyielding strength of a wild boar. The exact historical development is uncertain, but the association with resolute strength is well established.
The left side 豙 looks like a fierce boar standing its ground, and the right side 殳 is a weapon. Together they show a boar armed with determination—strong and unyielding.
For キ, imagine a strong key that never bends: key -> キ, and the key's unbreakable strength matches 毅's resolute spirit.