beautiful jade, star
璇 centers on a precious, luminous quality: a type of beautiful jade, and by extension a star, likely because of the gem-like brilliance of stars in the night sky.
璇 combines the jade radical 王 with 旋, which likely provides the sound and may contribute a sense of revolving or turning, perhaps alluding to the revolving stars or the polished surface of jade. The exact historical development is uncertain.
The jade radical 王 on the left suggests a precious stone. Picture a beautiful jade ornament carved with a swirling pattern like a revolving star, linking the gem to the star meaning.
For セン, imagine a beautiful jade star worth a thousand (千, せん) coins: 千 -> セン, and the star shines like polished jade.
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