desert, border prairie, the 1st form is radical 13
冋 centers on a remote open space: a desert or border prairie. The radical sense is the same visible shape used as a component in other characters.
冋 is an ancient character whose exact historical development is uncertain. It likely depicted a border or remote area, but the component origin is not clearly established.
The outer 冂 suggests a wide boundary, and the inner 口 looks like a small settlement or marker. Picture a lone outpost in a vast desert prairie.
For キョウ, imagine a border prairie so remote that the only sound is a distant echo: キョウ… キョウ… The echo cues the reading while the empty landscape reinforces the meaning.