ark shell
蚶 refers specifically to the ark shell, a type of bivalve mollusk. The meaning is narrow and concrete, with no broader conceptual extensions.
蚶 combines 虫 (insect/creature) with 甘, which likely contributes a phonetic element. The character is used for a type of shellfish, fitting the creature radical.
The left side 虫 suggests a small creature, and the right side 甘 (sweet) hints at the sweet meat of the ark shell. Picture a sweet little shellfish: 蚶.
For カン, imagine opening a can of ark shells: can -> カン, and inside the can you find the sweet shellfish.
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