A confidant is one to whom secrets are entrusted. The word comes, via French, from the Italian confidente, meaning "trusting, having trust in," from Latin confīdere, meaning "to put one’s trust in, have confidence in.” Other descendants of confīdere in English include confide, confidence, confident, and confidential, all of which ultimately have Latin fīdere, meaning "to trust (in), rely (on)," as their root. Confidant (and its variant confidante, used especially of a woman) and confident are often confused.

Source: Merriam-Webster