Why Do We Say “O’Clock” …The Surprising History Behind a Word We Use Every Day
English is full of fascinating quirks. Words that look like they should rhyme—such as come and home or through and cough—don’t. Other words, like tear and tear or wound and wound, are spelled the same but have completely different pronunciations depending on their meaning.
Then there are colorful expressions like “raining cats and dogs” or “going cold turkey,” which make perfect sense to native speakers but leave many language learners scratching their heads.
One everyday word that rarely gets a second thought is o’clock. We use it constantly when telling time, but have you ever wondered what the “O'” actually stands for?
The answer is rooted in centuries of English history.
What Does “O’Clock” Mean?
The “O'” in o’clock is a contraction of “of the.”
So when you say:
It’s three o’clock.
You’re actually using a shortened version of the older phrase:
It’s three of the clock.
In other words, you’re saying the time is three according to the clock.
Today, that wording sounds unusual, but hundreds of years ago it was perfectly normal.
Why Was “Of the Clock” Necessary?
Before mechanical clocks became common, people relied on the sun to tell time.
They used:
- Sundials
- Water clocks
- Candle clocks
- Hourglasses
- Natural shadows
As mechanical clocks spread across Europe during the late Middle Ages, people began distinguishing time shown by a clock from other ways of estimating the hour.
Saying “of the clock” simply meant the time being referred to was the one shown on the mechanical clock.
How “Of the Clock” Became “O’Clock”
Languages naturally become more efficient over time.
Frequently used phrases often get shortened because people tend to drop words that aren’t heavily stressed in everyday conversation.
Instead of repeatedly saying:
Five of the clock
people gradually began saying:
Five o’clock
Eventually, the shortened version became the standard expression, while the original phrase disappeared from everyday speech.
This process isn’t unique to English—it’s something that happens in languages all over the world.
