Mountain in Gansu province
峝 is a rare kanji that refers to a specific mountain in Gansu province. Its meaning is a proper place name with no broader conceptual center.
峝 combines 山 (mountain) with 同, which likely contributes the sound. It was created as a specific place name for a mountain in Gansu.
The top 山 means mountain, and the bottom 同 looks like a container. Picture a mountain shaped like a container in Gansu province.
For トウ, imagine a toe-shaped peak on the mountain: toe -> トウ, and that toe marks the mountain in Gansu.