Idioms about secrecy are as colourful and varied as secrets themselves. They reflect our human impulse to conceal, and our occasional blunders in the art of discretion. Let’s delve into some of these linguistic gems and explore how they describe the complexities of keeping (or spilling) secrets.
Mum’s the word
In this expression, “mum” has nothing to do with a mother or an Egyptian mummy. It is imitative of an inarticulate sound made with closed lips and means “silent” in Middle English. The word can be found in some of Shakespeare’s works, such as Henry VI, where the treacherous priest John Hume declares, “Seal up your lips and give no words but mum.” By the 17th century, “mum’s the word” had entered common usage as a colloquial exhortation to maintain secrecy.
During World War II, the idiom found new life in the British government’s “Careless Talk Costs Lives” campaign. Slogans like “Be like Dad, keep Mum” and “Keep Mum, she’s not so dumb” used wordplay to warn civilians and servicemen against divulging sensitive military information, while also reflecting broader societal attitudes towards women. Such patronising language stands in stark contrast to the reality of the time, as countless women—including the unsung heroines involved in the codebreaking operation at Bletchley Park—demonstrated extraordinary intelligence and discretion in wartime efforts, shattering stereotypes through their pivotal contributions.
Keep it under your hat
Why a hat? One theory suggests that it symbolises the head—a repository for thoughts safely concealed from prying eyes. Originating in 19th-century Britain, this phrase initially meant to keep an idea to oneself. By the time it crossed the Atlantic, its meaning had evolved to keeping confidences.
A famous practitioner of the idiom in the real sense was Abraham Lincoln who had the peculiar habit of using his stovepipe hat as a briefcase, literally keeping important documents in the lining. This historical nugget adds a touch of whimsy to the expression that continues to be a practical and poetic way to emphasise confidentiality.
On the QT
If discretion is paramount, you might urge one to keep something “on the QT”, in which QT is a shortened form of “quiet”. Some speculate that its roots lie in the Latin phrase quae tacenda, meaning “things that must not be spoken of”.
Modern usage varies, with some styling it as “on the q.t.” with periods and lowercase letters, while others prefer the uppercase abbreviation. Take this example from the New York Post: “Rich women across the world have a secret way of making big bucks: selling their castoffs on the QT.”
Spill the beans
The origins of “spill the beans” are murky, but a popular theory links it to ancient Greek voting practices, where beans were placed in jars to signify choices. If someone knocked over the jar, the results would be revealed prematurely.
By the 20th century, the phrase had expanded to describe any situation where someone upset the status quo by revealing information. Today, it is often used in a light-hearted manner, especially when coaxing someone to reveal a juicy titbit, as in “Come on, spill it”.
Loose lips sink ships
This phrase emerged during World War II as part of a US propaganda campaign warning that careless talk could bring calamities. Congressman Andrew May learned this lesson the hard way. After returning from a tour of the war zone in 1943, he inadvertently told the press that Japanese depth charges were set too shallow to threaten US submarines. The adversary took note and adjusted its tactics, allegedly resulting in significant American losses.
Although its wartime context is long gone, “loose lips sink ships” remains a powerful caution against reckless gossip in everyday life. These days, loose lips are more likely to sink friendships than battleships.
Secrets—whether kept or spilled—are part of what makes us human. Whether you are urged to “keep mum”, asked to “keep it under your hat” or tempted to “spill the beans”, remember: secrets are like toothpaste—once out, they can never be put back in.
