the body, substance, object, reality
躰 centers on the physical body as a tangible substance or object, extending to the idea of reality or concrete form.
躰 combines 身 (body) with 本 (origin, root), likely expressing the body as the fundamental physical substance. The exact historical development is uncertain.
The left side 身 is the body, and the right side 本 is the root or origin. Together they suggest the body as the root of physical substance and reality.
For タイ, imagine tying a rope around the body to measure its substance: tie -> タイ, and the body is the object being measured.
taidō (martial art)