Ingenuous (adjective)

1. Naive and innocent, showing a lack of sophistication.
2. Candid, honest and straightforward.

Origin:

This word comes from the latin word ingenuus, which means "native, innate, natural," and literally refers to someone who is not a slave or a freedman; it was later used to mean "free-born, legitimate" and then "noble, honorable" and in modern english it means "naive, innocent and candid". .

Examples:

1. He gave an ingenuous explanation for his behavior.
2. She had an ingenuous smile that made her approachable.
3. His ingenuousness was refreshing in a world of cynicism.
4. He was ingenuous enough to believe the con artist's story.
5. She was ingenuous in her dealings with the press.