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      hydrogen has been replaced by the amido group.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]