shrimp
魵 centers on shrimp, a small aquatic creature. The meaning is straightforward and specific.
魵 combines 魚 (fish) with 分, which likely contributes the sound. The character is rare, and its exact historical development is uncertain.
The left side is a fish 魚, and the right side 分 suggests dividing or a part. Picture a fish that is divided into small parts, like a shrimp segmented into pieces.
For フン, imagine a fun shrimp party where everyone is having fun eating shrimp: fun -> フン.