* Confide: To tell someone a secret or private matter, trusting them to keep it confidential.
* Fidelio: A person who is faithful or loyal.
* Fiduciary: Relating to trust, especially with regard to the holding of something in trust for another person.
* Infidel: A person who does not believe in a particular religion, especially one that is considered to be the true or correct religion.
* Infidelity: The act of being unfaithful to a spouse or partner.
* Confident: Feeling or showing certainty about something; having trust in oneself or one's abilities.
* Confidentiality: The state of being secret or private; the quality of being trusted.
Let me know if you'd like more examples or want to explore other suffixes!