/lɛt/
[verb] To allow someone to do something, or to give permission for something to happen. It can also mean to rent out a property to someone.
The word 'let' once meant the exact opposite — to hinder and block — which is why tennis still uses the old meaning today.
Few words in the English language carry such a fascinating contradiction within them. The modern verb 'let' — meaning to allow or permit — descends from the Old English word 'lǣtan', which meant to leave behind, release, or allow to go. It comes from the Proto-Germanic root 'lētaną', and before that from the Proto-Indo-European root 'lēd-', meaning to let go or release. This sense of releasing or freeing something has remained at the heart of the word for over a thousand years.
But here is where the story takes a remarkable turn. Old English also contained a completely different word: 'lettan', meaning to hinder, obstruct, or prevent. This word came from a separate Proto-Germanic root, 'latjaną', which is connected to the adjective 'læt' — meaning slow or late. To 'let' something, in this older sense, was to slow it down, to put an obstacle in its path. These two words — 'lǣtan' (to allow) and 'lettan' (to hinder) — were near-opposites living side by side in the same language, distinguished only by a slight difference in vowel length.
Over the centuries, as English shifted and simplified through the Middle English period, 'lettan' gradually faded from everyday use. But it did not disappear entirely. It survived in legal language — a 'let or hindrance' was a formal phrase in contracts and law — and most famously, it survived in sport. In tennis, a 'let' is called when a serve clips the net and must be replayed. The net has 'hindered' the ball. This is the ancient word 'lettan' still alive and in use today, preserved like an insect in amber while the rest of the language moved on around it.
The permissive sense of 'let', from Old English 'lǣtan', evolved steadily through Middle English as 'leten' and then into the modern form. By the 14th and 15th centuries, it was firmly established in the sense of allowing or permitting, appearing in texts ranging from religious writing to everyday correspondence. Its connection to related words is clear: Old English 'lǣtan' → Middle English 'leten' → Modern English 'let'. The same Proto-Germanic root 'lētaną' also gave us the word 'late', through Old English 'læt', meaning slow or behind time — the sense of something being held back or released too slowly.
The property-rental meaning of 'let' — as in a 'holiday let' or 'to let a flat' — grew naturally from the sense of releasing or giving over something to another person. To let a room was to release it into someone else's use. This usage is particularly common in British English and has been in steady use since at least the 16th century. Landlords in Victorian England would hang signs reading 'To Let' outside empty properties, a phrase that still appears on rental signs across Britain today.
What makes 'let' so remarkable is not just its age, but the way it contains its own history — a word that once meant stop now means go, and yet the old meaning lingers in the one corner of modern life where a small rubber ball hits a piece of net. In this way, language behaves like geology: the surface is smooth and modern, but if you know where to look, the ancient strata are still there, just beneath.