swear somebody to secrecy
swear (one) to secrecy
To make one promise that they won't reveal something that they know about. The company swore me to secrecy before promoting me to work on their latest product. OK, I'll tell you, but I have to swear you to secrecy!
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
swear somebody to ˈsecrecymake somebody promise not to tell a secret: Before telling her what happened, I had sworn her to secrecy. ♢ Everyone was sworn to secrecy about what had happened.
Farlex Partner Idioms Dictionary © Farlex 2017