the.com/puffer fish

means A slow-swimming fish that, when threatened, gulps water (or air) to inflate into a round, often spine-studded ball too big and awkward to swallow — and in many species packs a neurotoxin lethal enough to kill a predator that tries anyway.

from The name is just plain descriptive English — it 'puffs' up — attached straightforwardly to 'fish,' with no hidden backstory. The more interesting etymology lives in its scientific family name, Tetraodontidae, from Greek tetra- ('four') and odous ('tooth'), describing the four large tooth plates fused into a beak-like structure it uses to crush shellfish. The toxin it often carries, tetrodotoxin, borrows that same root.