“Sensei, the skin is what gives the fish its name?”

“That’s right.”

“And the first thing you notice is that horn.”

“A spine on the dorsal fin.“

“So the skin gives it a name, the spine catches your eye, and come winter, it’s the liver?”

“Exactly. The liver’s the whole point.”

Kawahagi (filefish), from Mōri Baien’s Baien Gyofu. Edo period.

National Diet Library, Japan.

Kawahagi, or filefish, takes its Japanese name from its thick, rough skin, which peels away.

皮 (kawa) means “skin,” and はぎ (hagi) means “peeling off.” It comes from the verb はぐ (hagu), “to peel off.”

Just behind the eye, a spine on the dorsal fin sticks up like a horn. The fish has mild white flesh, and its liver grows larger in winter.