cod liver

from The Collaborative International Dictionary of English v.0.48

Cod liver \Cod" liv`er\, n.
   The liver of the common cod and allied species.
   [1913 Webster]

   {Cod-liver oil}, an oil obtained from the liver of the
      codfish, and used extensively in medicine as a means of
      supplying the body with fat in cases of malnutrition.
      [1913 Webster]