This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
玵 combines 王 (jade/jewel) with 甘 (sweet). The exact historical development is uncertain, but it likely relates to a type of jade or precious stone.
The left side 王 suggests a jewel, and the right side 甘 suggests sweetness. Imagine a sweet, lustrous gemstone, but its exact meaning is unclear.
For ガン, picture a gun made of jade: gun -> ガン, a rare and precious weapon.
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