keep it/something dark
keep (something) dark
To hide or withhold knowledge of something from others; to keep something secret. Unfortunately, when you collaborate with large corporations, there is a lot of information they make you keep dark. She somehow managed to keep their relationship dark for over a year.
keep something dark
If you keep something dark, you keep it a secret. She took pleasure in keeping dark the identity of the man who was coming.
keep something darkkeep something secret from other people.
1993 New York Review of Books Ottoline was determined to keep her affair with Russell safe from Bloomsbury's prying eyes and she and Russell went to Feydeauesque lengths to keep their secret dark.