confidence

Concise Oxford English Dictionary © 2008 Oxford University Press:
confidence/ˈkɒnfɪdəns/

▶noun

• 1 the belief that one can have faith in or rely on someone or something.

  ■ a positive feeling arising from an appreciation of one's own abilities; self-assurance.

• 2 the telling of private matters or secrets with mutual trust.

  ■ a secret or private matter told to someone under a condition of trust.

– phrases
in someone's confidence in a position of trust with someone.
take someone into one's confidence tell someone one's secrets.

– origin ME: from L. confidentia, from confidere (see confident).