the neck
脰 refers specifically to the neck, the part of the body connecting the head and torso.
脰 combines the flesh radical ⺼ with 豆, which likely provides the sound. The character was created to represent the neck.
The flesh radical ⺼ on the left suggests a body part, and 豆 on the right looks like a bean-shaped neck joint. Picture a bean-shaped neck supporting the head.
For トウ, imagine touching your neck with a toe: toe -> トウ, and the toe points to the neck.