stop, linger
竚 centers on standing still in one place: stopping movement and lingering there for a while.
竚 combines 立 (stand) with 宁, which likely contributes the sound and reinforces the idea of staying in place. The exact historical development is uncertain.
The left side 立 means stand, and the right side 宁 looks like a roof over a hook, suggesting staying under shelter. Picture someone standing under an awning, lingering and stopping for a while.
For チョ, imagine a person who stops to linger and says 'cho' as a soft sigh while standing still: cho -> チョ.