defining

secret (via google):

• not open or public; kept private or not revealed; "a secret formula"; "secret ingredients"; "secret talks"
• clandestine: conducted with or marked by hidden aims or methods; "clandestine intelligence operations"; "cloak-and-dagger activities behind enemy lines"; "hole-and-corner intrigue"; "secret missions"; "a secret agent"; "secret sales of arms"; "surreptitious mobilization of troops"; "an undercover investigation"; "underground resistance"
• unavowed: not openly made known; "a secret marriage"; "a secret bride"
• communicated covertly; "their secret signal was a wink"; "secret messages"
• not expressed; "secret (or private) thoughts"
• hidden: designed to elude detection; "a hidden room or place of concealment such as a priest hole"; "a secret passage"; "the secret compartment in the desk"
• privy: hidden from general view or use; "a privy place to rest and think"; "a secluded romantic spot"; "a secret garden"
• confidential: (of information) given in confidence or in secret; "this arrangement must be kept confidential"; "their secret communications"
• something that should remain hidden from others (especially information that is not to be passed on); "the combination to the safe was a secret"; "he tried to keep his drinking a secret"
• indulging only covertly; "a secret alcoholic"
• information known only to a special group; "the secret of Cajun cooking"
• mysterious: having an import not apparent to the senses nor obvious to the intelligence; beyond ordinary understanding; "mysterious symbols"; "the mystical style of Blake"; "occult lore"; "the secret learning of the ancients"
• mystery: something that baffles understanding and cannot be explained; "how it got out is a mystery"; "it remains one of nature's secrets"
• the next to highest level of official classification for documents

i like the communicated covertly (messages), indulging covertly (fetishism), and the veil of mystery.