move, stagger
蹌 centers on unsteady movement: moving in a staggering, reeling way, as if losing balance.
蹌 combines 足 (foot) with 倉, which likely contributes the sound. The exact historical development is uncertain, but the structure suggests a phono-semantic compound related to foot movement.
The left side is 足 (foot), and the right side 倉 looks like a storehouse. Imagine someone stumbling out of a storehouse, their feet staggering unsteadily.
For ソウ, picture a person staggering like a soul leaving the body: soul -> ソウ, and the feet move unsteadily.