agate
碯 refers specifically to agate, a type of banded gemstone.
碯 combines 石 (stone) with a phonetic component that likely contributed the sound ノウ. The exact historical development of the right side is uncertain.
The left side 石 means stone. Picture a stone with swirling bands inside, like the 巛 (river) shape trapped within a 囗 (enclosure), forming an agate.
For ノウ, imagine a stone that knows its own beauty: know -> ノウ, and this agate knows it is a gem.
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