This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
鼟 combines 鼓 (drum) and 登 (ascend), likely a phono-semantic compound where 登 contributes the sound and 鼓 suggests a drum-related meaning. The exact historical development is uncertain.
The top part 鼓 means drum, and the bottom part 登 means climb. Imagine a drumbeat that climbs in volume, but the exact meaning is uncertain.
For トウ, think of a toe tapping to a drum: toe -> トウ, and the drum 鼓 beats as you climb 登.
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