From moon +‎ fish, from the silvery color, parallel to the synonymous Dutch cognate maanvis.

moonfish (plural moonfish or moonfishes)

1. Any of various species of fish of a round appearance in several families:
   1. Any of species Mene maculata (razor moonfish), sole accepted, extant species of family Menidae, of tropical coastal waters of the Indo-Pacific area;
   2. A platyfish, of either of Xiphophorus maculatus or X. variatus (family Poeciliidae).

      Hyponym: common platy

   3. Any member of most species of the genera Selene and Paraselene (family Carangidae).
   4. Any of genus Lampris of opahs (family Lamprididae);
   5. Any of species Mola mola (common mola or ocean sunfish; family Molidae).

• African moonfish (Selene dorsalis)
• Atlantic moonfish (Selene setapinnis)
• Brown's Caribbean moonfish (Selene brownii)
• mariposa moonfish (Lampris guttatus)
• Mexican moonfish (Paraselene orstedii)
• ocean moonfish (Lampris guttatus)
• Pacific moonfish, Peruvian moonfish (Selene peruviana)
• razor moonfish (Mene maculata)
• sailfin moonfishs (Veliferidae spp.)
• silver moonfish (Neosilurus hyrtlii, Drepane punctata)
• southern moonfish (Lampris immaculatus)
• spotted moonfish (Lampris guttatus)

• moonyfishes (Monodactylus spp.)

• “moonfish”, in OneLook Dictionary Search.
• 👁 Image
  moonfish on Wikipedia.Wikipedia