big, ignorant, rude, rustic
侗 centers on a lack of refinement or knowledge: someone big and rustic, rude, or ignorant. The meanings describe a rough, unpolished person rather than a single clear conceptual thread.
侗 combines 亻 (person) with 同, which likely contributes the sound. The exact historical development is uncertain, but the character is associated with rustic or ignorant people.
A person 亻 who is the same 同 as everyone else in a rough, uneducated village: big, rustic, and ignorant.
For トウ, imagine a big, rude person stubbing their toe and shouting 'TOW!': toe -> トウ, and the pain makes them act even more rustic.