A Penny Turned the Latch
John Nevil Maskelyne’s pay-to-enter toilet lock made a small payment part of the door’s mechanism. A user inserted a penny into the lock; the coin’s movement released the latch, allowing the door to open. The coin was not simply collected as a fee after entry: it was the key that activated access.
That arrangement addressed a practical problem for public toilets: how to charge for use without stationing someone at every door. A coin-operated lock could collect payment automatically, one person at a time. It also made the cost immediate and visible: no penny, no unlocked door.
From Lock to Expression
The phrase “spend a penny” turned that everyday transaction into a polite euphemism for using a public toilet. “Spend” referred literally to handing over the coin, but the phrase let speakers avoid naming the bodily need directly.
Maskelyne was known as a magician, yet this invention belonged to the practical world of locks and mechanisms. Its legacy was not only a new way to control access; it left behind a bit of language in which an ordinary trip to the toilet still sounds like a tiny purchase.
