The Collaborative International Dictionary of English v.0.48:

Mammal \Mam"mal\, n.; pl. Mammals. [L. mammalis belonging to
   the breast, fr. mamma the breast or pap: cf. F. mammal.]
   (Zool.)
   One of the Mammalia.
   [1913 Webster]

   Age of mammals. See under Age, n., 8.
      [1913 Webster]