Definify.com

Webster 1913 Edition

Noun.

The state or quality of being ingenuous; openness of heart; frankness.

Ingenuity.

[Obs.]

Fuller.

Noun.

Openness of heart; frankness; fairness; freedom from reserve or dissimulation; as, to confess our faults with ingenuousness.

Fairness; candidness; as the ingenuousness of a confession.

ingenuousness ‎(countable and uncountable, plural ingenuousnesses)

The condition of being ingenuous.
(countable) An ingenuous behavior.
- Aldous Huxley
  Time passed; Moira grew up, chronologically; but Sir Watney went on treating her as a spoilt child, went on being enchanted by her birdy chirrupings and ingenuousnesses and impertinent enfant-terrible-isms.