madder
藘 refers specifically to the madder plant, a source of red dye. Its meaning is narrow and botanical, without broader abstract extensions.
藘 combines the grass radical 艹 with 慮, which likely provides the sound. The character was created to name the madder plant, but the exact historical development is uncertain.
The grass radical 艹 sits above 慮, a component associated with thought. Picture a thoughtful herbalist carefully tending a madder plant, knowing its roots will yield a rich red dye.
For リョ, imagine a madder plant growing beside a ryokan (旅館, りょかん), its red roots matching the inn's crimson sign: ryokan -> リョ.
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