The Collaborative International Dictionary of English v.0.48:

Hypogaeic \Hyp`o*g[ae]"ic\, a. [Pref. hypo- + Gr. gai^a, gh^,
   earth.] (Chem.)
   Pertaining to, or obtained from, the peanut, or earthnut
   (Arachis hypog[ae]a).
   [1913 Webster]

   Hypog[ae]ic acid (Chem.), an acid in the oil of the
      earthnut, in which it exists as a glyceride, and from
      which it is extracted as a white, crystalline substance.
      [1913 Webster]