under lock and key: Idiom Meaning and Origin

The idiom "behind closed doors" is closely related to the concept of something being "under lock and key." When something is said to be happening "behind closed doors," it means that it is taking place in private, away from public view or scrutiny. This idiom implies a sense of secrecy or confidentiality, similar to the idea of something being locked away and protected. It suggests that there may be hidden or undisclosed information or actions taking place, and that access to such information or actions is restricted to a select group of people.

In a symbolic sense, being "behind closed doors" can also refer to situations or discussions that are kept confidential, such as negotiations, decision-making processes, or sensitive conversations. Just like something that is under lock and key, matters that happen behind closed doors are not easily accessible or known by everyone. This idiom emphasizes the idea of limited access and the need for discretion.

Another related idiom is "Fort Knox." When something is described as being as secure as "Fort Knox," it means that it is extremely well-protected and difficult to access or breach. Fort Knox is the United States Bullion Depository, a highly secure facility that stores a large portion of the country's gold reserves. The comparison to Fort Knox suggests that whatever is being referred to in the context of the idiom is similarly impervious to unauthorized entry or tampering. This reinforces the concept of something being under lock and key, under tight security measures that ensure its protection and safety.

"in a box" is another idiom that is closely related to the notion of something being "under lock and key." When something is said to be "in a box," it means that it is enclosed or sealed within a container of some sort. This implies a level of confinement, isolation, and inaccessibility. Just like something that is under lock and key, an item that is in a box is secured and protected, often from the outside world or from potential damage. This idiom invokes the idea of boundaries and restricted access, emphasizing the need for careful handling and safeguarding.

Finally, the idiom "closed book" is also relevant to the concept of something being "under lock and key." When something is described as a "closed book," it means that it is difficult or impossible to understand or access. This idiom conveys a sense of mystery, secrecy, or inaccessibility. Just like something that is under lock and key, a closed book is closed off and kept from view or comprehension. It suggests that information or knowledge is being withheld or concealed, and that access to it is limited. This idiom underscores the idea of something being hidden or restricted, adding to the overall theme of safeguarding and protection that is associated with being "under lock and key."