step on, trample, carry through, appraise, evade payment
蹈 centers on the action of stepping or treading, with extended uses for carrying through an action, appraising by stepping through a process, and evading payment by figuratively stepping over obligations.
蹈 combines 足 (foot) with 舀, which likely contributes the sound and relates to stepping or treading. The exact historical development of 舀 is uncertain.
The left side 足 means foot, and the right side 舀 looks like a hand reaching into a container. Imagine stepping forward with your foot to reach into a situation, trampling obstacles and carrying through.
For トウ, picture a toe stepping firmly on the ground: toe -> トウ, and your foot tramples down.