This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
鞖 combines 革 (leather) with 妥, but the exact historical development and original meaning are uncertain.
The left side is leather 革, and the right side is 妥 (gentle, peace). Picture a soft leather item that brings comfort, but remember its standalone meaning is unclear.
For サイ, imagine a sigh of relief when you touch the soft leather: sigh -> サイ.
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