matting, coverlet, cloudy
絪 centers on a thick, soft covering or layer: a mat, a coverlet, or a cloudy haze that blankets the sky.
絪 combines 糸 (thread) with 因, which likely contributes the sound. The character originally referred to a woven mat or coverlet, and the cloudy sense extends from the idea of a thick, enveloping layer.
Thread 糸 wrapped around 因 creates a thick woven mat or coverlet. Imagine a dense fabric so heavy it feels like a cloudy blanket.
For イン, picture an inn with a thick woven mat at the entrance: inn -> イン, and the mat is made of thread.
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