arrow-tip
砮 centers on the sharp tip of an arrow, specifically the arrowhead. It refers to the pointed striking end of an arrow.
砮 combines 石 (stone) with 奴, which likely contributes the sound. The character originally referred to a stone arrowhead, reflecting the material and the weapon.
The bottom 石 is stone, and the top 奴 suggests a tool or weapon. Picture a stone arrowhead chipped from rock: 砮 is the sharp stone tip of an arrow.
For ド, imagine a stone arrowhead striking a door with a loud 'do' sound: door -> ド, and the stone tip hits the target.