walk, go on foot, run, leave
赱 centers on movement by foot: walking, running, or going on foot. The sense of leaving is a natural extension of moving away on foot.
赱 is a variant form of 走, which originally depicted a person running with a foot below. The top 土 is a simplification of the running figure, and the lower part suggests the foot.
The top 土 looks like a person's upper body, and the lower strokes resemble legs in motion. Picture someone striding across the earth: 赱 is walking or running.
For ソウ, imagine a person walking so fast they create a 'sow' sound as their feet brush the ground: sow -> ソウ, and they're off on foot.