type of tree
朷 refers to a type of tree. The given meaning is narrow and specific, so the core idea is simply a particular kind of tree.
朷 combines 木 (tree) with 刀 (knife), likely as a phono-semantic compound where 刀 hints at the sound and 木 gives the meaning category. The exact historical development is uncertain.
A tree 木 beside a knife 刀: imagine a tree whose wood is so hard you need a knife to carve it, marking it as a distinct type of tree.
For トウ, picture a toe-shaped leaf on this special tree: toe -> トウ, and the tree is known for its toe-like leaves.
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