blowfish, globefish, spheroides vermicular
魨 centers on a specific type of fish: the blowfish or globefish, known for its ability to inflate. The meanings all refer to this same puffer-like fish.
魨 combines 魚 (fish) with 屯, which likely contributes the sound トン. The character was created to name the blowfish.
The left side 魚 means fish, and the right side 屯 looks like a puffed-up body with a cross inside. Picture a fish that inflates into a round, spiky ball: the blowfish.
For トン, imagine a ton of blowfish piled up: ton -> トン, and the fish radical reminds you it's a fish.