CONFIDANT
confidant, intimate
(noun) someone to whom private matters are confided
Source: WordNet® 3.1
Etymology
Noun
confidant (plural confidants)
A person in whom one can confide or share one's secrets: a friend.
Source: Wiktionary
Con`fi*dant"; 277), n. masc., Con`fi*dante", n. fem.Etym: [F.
confident, confidente, formerly also spelt confidant, confidante. See
Confide, and cf. Confident.]
Definition: One to whom secrets, especially those relating to affairs of
love, are confided or intrusted; a confidential or bosom friend.
You love me for no other end Than to become my confidant and friend;
As such I keep no secret from your sight. Dryden.
Source: Webster’s Unabridged Dictionary 1913 Edition