This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 蒅 is uncertain. It visually combines 艹 (grass) with 染 (dye), but the original meaning and component relationship are unclear.
The top grass radical 艹 sits above 染 (dye), suggesting something related to plant dyeing, but the actual meaning is uncertain.
For すくも, imagine soaking (すく) a plant in dye until it becomes dark and murky (も), like the color of sumi ink: すくも.
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dye made of fermented indigo leaves