hoof
蹏 centers on the hoof of an animal, the hard foot part that touches the ground.
蹏 combines 足 (foot) with 虒, which likely contributes the sound and may relate to an animal or hoof-like shape. The exact historical development of 虒 is uncertain.
The left side 足 means foot, and the right side 虒 looks like a complex animal shape. Picture a horse's foot with a hard hoof: 蹏 is that hoof.
For テイ, imagine a horse's hoof tapping the ground with a clear 'tay' sound: tay -> テイ, and the hoof strikes the earth.