We say “o’clock” countless times without thinking about what the word actually means. Yet the small “O” has a history that goes back hundreds of years. The word is a shortened form of the older phrase **“of the clock.”** So, when people once said “It’s three of the clock,” they simply meant that it was three according to the time shown by a clock.
Before mechanical clocks became common, people used sundials, water clocks, hourglasses, candles, and the position of the sun to estimate the time. As mechanical clocks became more widespread during the Middle Ages, saying “of the clock” helped make it clear that the time came from a clock rather than another method.
Over time, everyday speech naturally became shorter. Instead of saying “five of the clock,” people gradually began saying **“five o’clock.”** The longer version eventually disappeared, but the shortened expression remained part of English. The apostrophe in “o’clock” is a small reminder of those missing words.
English contains many other expressions that preserve similar pieces of its past. **“Jack-o’-lantern,” “will-o’-the-wisp,”** and **“ne’er-do-well”** all contain older shortened forms. These words show how frequently used expressions can change while still keeping traces of their original structure.
The next time you say “It’s six o’clock,” you’re using a phrase with centuries of history behind it. What sounds like a simple letter is actually a shortened form of **“of the clock.”** It’s a fascinating reminder that everyday language is constantly changing, and even the smallest words can carry stories from the past.