These four walls phrase spoken
Literally, it means the room you are in, but figuratively it is used to mention a secret that someone doesn't want to be told to anyone else.
This matter can only be discussed within these four walls.
You must not let our conversation go further than these four walls.
This little secret between us must not be repeated outside these four walls.
Used to tell someone to keep secret what you're about to say
Kept in secret
When two individuals desire to be alone with each other, a third person is not welcome.
To secretly punish or rebuke someone for doing something.
A place or condition in which there is no privacy.
Used to allude that the last force, problem or burden which is seemingly minor and small causes a person, system or organisation to collapse or fail
Her husband's violent act last night was the straw that broke the donkey's back and she left him