jewel
琿 centers on a jewel or gem, specifically a type of precious stone. The meaning is narrow and concrete, referring to a valuable ornamental mineral.
琿 combines 王 (jade, jewel) with 軍, which likely provides the sound コン. The character is a phono-semantic compound where the left side indicates the meaning and the right side suggests the reading.
The left side 王 is the jewel radical, and the right side 軍 looks like a military vehicle. Imagine a jewel-encrusted war chariot: the jewel is the precious stone 琿.
For コン, picture a con artist trying to sell a fake jewel: con -> コン, and the jewel is the 琿.
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