a method of dyeing
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繝 centers on a specific dyeing technique, referring to a method of applying color to fabric.
ungen; method of dyeing in which a color repeatedly goes from dense to diffuse, diffuse to dense; used in Buddhist pictures, temple ornaments, etc., during the Nara and Heian periods
繝 combines 糸 (thread, textile) with 閒, which likely contributes the sound and relates to the dyeing process. The exact historical development is uncertain.
The left side 糸 suggests thread or fabric, and the right side 閒 looks like a gate or space. Imagine dye being carefully applied through a gap in a stencil onto silk threads.
For カン, picture a can of dye being poured over the fabric: can -> カン, and the thread soaks up the color.