must, certain

必 is composed of a variant of 戈 (dagger-axe) and two strokes. The two strokes are located on either side of the handle, conveying the idea of two hands tightly gripping the wooden handle of a dagger-axe. Its original meaning is the handle of a weapon, but this sense was later taken over by 柲. When fighting with a dagger-axe, one must grip the wooden handle tightly; otherwise the weapon will fall. Therefore, 必 is used to mean must or certain.