exterior rim of wheel
輮 centers on the outer rim of a wheel, the curved wooden part that forms the wheel's circumference.
輮 combines 車 (vehicle, wheel) with 柔 (soft, pliable), likely referring to the process of bending wood to form a wheel rim. The exact historical development is uncertain.
The left side 車 is a vehicle or wheel, and the right side 柔 suggests something pliable. Picture a flexible strip of wood being bent around a wheel frame to form the outer rim.
For ジュウ, imagine a jeweler carefully bending a metal rim onto a wheel: jeweler -> ジュウ, and the rim fits perfectly.