block of wood, blockhead, stupid
梼 centers on a block of wood and, by extension, a blockhead or stupid person—someone as dense and unresponsive as a wooden block.
梼 combines 木 (tree/wood) with 寿, which likely contributes the sound. The meaning 'block of wood' fits the wood radical, and the extended sense 'blockhead' is a metaphorical use.
A wooden block (木) beside a shape suggesting longevity (寿) — imagine an old, stubborn block of wood that has sat around so long it has become dense and stupid.
For トウ, picture a toe (トウ) stubbed on a block of wood: the pain makes you feel like a blockhead for not watching where you were going.
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