the bottle-gourd
瓟 refers specifically to the bottle-gourd, a type of gourd plant or its fruit, often used as a container.
瓟 combines 瓜 (gourd) with 包 (wrap), likely indicating a gourd used as a wrapping or container. The exact historical development is uncertain.
A gourd 瓜 wrapped 包 around itself forms a natural bottle: the bottle-gourd.
For ハク, imagine a bottle-gourd being hacked open to make a container: hack -> ハク.
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