clam
蚌 centers on a bivalve mollusk: a clam. The meaning is concrete and specific to this shellfish.
蚌 combines 虫 (insect/creature) with 丰, which likely contributes a phonetic element. The character refers to a clam, a shelled creature.
The left side 虫 suggests a small creature, and the right side 丰 looks like a shell with lines. Together they form a clam: a creature with a lined shell.
For ボウ, imagine a bow-shaped clam shell opening and closing: bow -> ボウ, and the clam creature inside.