Etymology

Attested in Pliny the Elder's Natural History as a word for a large fish from the Rhine, but otherwise only in New Latin, applied by Linnaeus to a pike. Most likely, the scant Classical references to a fresh-water fish indicate that the word was borrowed from Celtic Transalpine Gaulish *esoks (compare Irish eó ‎(“salmon”), Welsh ehawc ‎(“salmon”)); usually also compared is Ancient Greek ἴσοξ ‎(ísox, “unknown whale-like fish”), attested only in a vocabularly list.