Comprehensive resource for understanding and mastering English idioms
The idiom "behind closed doors" refers to a situation or conversation that is kept secret or hidden from the public eye, often because it is considered private or confidential. It suggests a clandestine or illicit activity taking place in a room where others are not present.
The origin of this idiom is uncertain, but it has been in use since the 17th century. One theory suggests that it comes from the medieval practice of hiding illegal activities or contraband items behind closed doors. Another theory is that it refers to secret meetings or discussions held in private rooms during political campaigns or other important events. Over time, the meaning and usage of this idiom have evolved slightly. It has come to be used more broadly to refer to any situation or conversation that is kept secret or hidden from others, even if it is not necessarily illicit or illegal.