confidential

Etymology

From Latin confidentia + -al.

adj

1. Kept, or meant to be kept, secret within a certain circle of persons; not intended to be known publicly
   (obsolete)
   The newspaper claims a leaked confidential report by the government admits to problems with corrupt MPs.
   […] I have a communication of a very private—indeed, I will say, of a sacredly confidential nature, which I desire to make to you. 1872, George Eliot, Middlemarch, Edinburgh: William Blackwood, Book 6, Chapter 61, p. 355
   It would tell against your reputation, losing a confidential document, wouldn’t it? Why didn’t you keep it confidential if it was confidential? 1960, Muriel Spark, chapter 10, in The Bachelors, Philadelphia: Lippincott, published 1961, page 163
2. (dated) Inclined to share confidences; (of things) making people inclined to share confidences; involving the sharing of confidences.
   Sitting in front of the fire, they became quite confidential, and began to gossip.
   She and Bertha had never been on confidential terms, but at such a crisis the barriers of reserve must surely fall: 1905, Edith Wharton, The House of Mirth, New York: Scribner, Book 2, Chapter 2, p. 329
   Miss Raste was encouraged to be entirely confidential, to withhold nothing even about herself, by the confidence-inspiring and kindly aspect of Elsie’s face. 1923, Arnold Bennett, Riceyman Steps, London: Cassell, Part 5, Chapter 2, p. 241
3. (dated) Having someone's confidence or trust; having a position requiring trust; worthy of being trusted with confidences.
   a confidential agent; a confidential servant; a confidential whisper
   This paper will serve instead of a confidential friend into whose ear I might pour forth the overflowings of my heart. 1848, Anne Brontë, chapter 18, in The Tenant of Wildfell Hall, volume 1, London: T.C. Newby, pages 320–321
   I repeated the instruction by letter and I kept a copy of the letter witnessed by my confidential maid. 1924, Ford Madox Ford, Some Do Not ..., London: Duckworth, Part 2, Chapter 2, p. 245
   “He said he was a confidential messenger,” shouted a man. 1959, Kurt Vonnegut, chapter 6, in The Sirens of Titan, New York: Dial, published 2006, page 155