confidant
Concise Oxford English Dictionary © 2008 Oxford University Press:
confidant /ˈkɒnfɪdant, ˌkɒnfɪˈdant, -dɑːnt/
▶noun (fem. confidante pronunc. same) a person in whom one confides.
– origin C17: alt. of confident (as a noun in the same sense), prob. to represent the pronunc. of Fr. confidente ‘having full trust’.
'confidant' also found in these Oxford entries:

