balance weights
砝 centers on the idea of balance weights used in scales or measuring. It refers to the physical weights that counterbalance objects to determine their mass.
砝 combines 石 (stone) with 去, likely indicating a stone weight used for balancing. The exact historical development is uncertain, but the character is associated with weighing.
A stone (石) that goes away (去) from the center of a scale to find balance: 砝 is a balance weight.
For キョウ, imagine a balance weight shaped like a tiny Kyoto tower: Kyoto -> キョウ, and the stone weight keeps the scale balanced.