blowfish
鯺 centers on the blowfish, a specific type of fish known for its ability to inflate and its toxic properties.
鯺 combines 魚 (fish) with 者, which likely contributes the sound. The exact historical development is uncertain, but the structure suggests a phono-semantic compound for a type of fish.
The left side is a fish 魚, and the right side 者 looks like a person sitting. Imagine a person puffing up their cheeks like a blowfish.
For ショ, picture a blowfish showing off its spikes: show -> ショ, as the fish puts on a show.