a kind of cloth
襴 refers to a specific type of cloth, likely a patterned or bordered fabric used in traditional garments.
襴 combines the cloth radical 衤 with 闌, which likely contributes the sound and may relate to a patterned or bordered design. The exact historical development is uncertain.
The left side 衤 is clothing, and the right side 闌 looks like a gate with a sun and tree inside. Imagine a special cloth with a gate-like pattern woven into it, used for ceremonial robes.
For ラン, picture a long run of this special cloth being unrolled: run -> ラン, and the cloth stretches out in a long, patterned strip.
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