Source : Webster's Revised Unabridged Dictionary (1913)

Ingenuousness \In*gen"u*ous*ness\, n.
   1. The state or quality of being ingenuous; openness of
      heart; frankness.

   2. Ingenuity. [Obs.] --Fuller.

Source : WordNet®

ingenuousness
     n 1: the quality of innocent naivete [syn: {artlessness}, {innocence},
           {naturalness}]
     2: openly straightforward or frank [ant: {disingenuousness}]