confidant

 
Pronunciation: /ˈkɒnfɪdant, ˌkɒnfɪˈdant, -dɑːnt/

noun (feminine confidante pronunc. )

  • a person with whom one shares a secret or private matter, trusting them not to repeat it to others: a close confidante of the princess

Origin:

mid 17th century: alteration of confident (as a noun in the same sense in the early 17th century), probably to represent the pronunciation of French confidente 'having full trust'