stone resembling jade, agate
瑀 centers on a type of ornamental stone: a stone that resembles jade, or agate. It is a specific gemstone name rather than a broad concept.
瑀 combines 王 (jade) with 禹, which likely contributes the sound. It refers to a specific type of stone or agate.
The left side 王 is the jade radical, and the right side 禹 looks like a creature with a shell. Imagine a stone that looks like jade but has a pattern resembling a turtle shell, like agate.
For ウ, imagine a beautiful agate stone that makes you say 'Ooh!' in admiration: 'Ooh' -> ウ.
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