oak
椈 centers on a type of tree: specifically, an oak. The meaning is a single concrete botanical reference.
椈 combines 木 (tree) with 匊, which likely contributes the sound. The character was created to name a specific tree, the oak.
The tree radical 木 beside 匊 suggests a particular kind of tree. Picture a sturdy oak with its characteristic leaves and acorns.
For キク, imagine a key carved from oak wood that you keep in a cool, quiet nook: key-cool -> キク, and the oak key unlocks the forest.
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Japanese beech (Fagus japonica)