This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
絑 combines 糸 (thread) with 朱 (vermillion), suggesting a connection to red silk or thread, but the exact historical development is uncertain.
The left side 糸 suggests thread or fabric, and the right side 朱 is associated with vermillion red. Picture a bolt of red silk, though the kanji's meaning is not firmly established.
For シュ, imagine a bolt of red silk being unrolled with a smooth 'shoo' sound: shoo -> シュ, like the hush of fine fabric.
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