Source : Webster's Revised Unabridged Dictionary (1913)

Butterfish \But"ter*fish`\, n. (Zo["o]l.)
   A name given to several different fishes, in allusion to
   their slippery coating of mucus, as the {Stromateus
   triacanthus} of the Atlantic coast, the {Epinephelus
   punctatus} of the southern coast, the rock eel, and the
   kelpfish of New Zealand.