outer box for a coffin
椁 refers specifically to the outer protective box or casing that encloses a coffin, a secondary container used in traditional burial practices.
椁 combines 木 (wood, tree) with 享, which likely contributes a phonetic element. The character denotes a wooden outer coffin casing, consistent with the material and function.
The left side 木 (wood) suggests the material, and the right side 享 looks like a sturdy container. Imagine a wooden outer box built to encase a coffin, protecting it like a shell.
For カク, picture a wooden outer coffin box shaped like a cube: cube -> カク, and the wooden box encloses the inner coffin.
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