The Collaborative International Dictionary of English v.0.48:

Amido \A*mi"do\, a. [From Amide.] (Chem.)
   Containing, or derived from, amidogen.
   [1913 Webster]

   Amido acid, an acid in which a portion of the nonacid
      hydrogen has been replaced by the amido group. The amido
      acids are both basic and acid.

   Amido group, amidogen, NH2.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Amidogen \A*mid"o*gen\, n. [Amide + -gen.] (Chem.)
   A compound radical, NH2, not yet obtained in a separate
   state, which may be regarded as ammonia from the molecule of
   which one of its hydrogen atoms has been removed; -- called
   also the amido group, and in composition represented by the
   form amido.
   [1913 Webster]