What is the full word for o clock?

The History of O'Clock

Ever wondered why we throw an apostrophe into the word o'clock when telling time? It actually comes from an old phrase used centuries ago to specify that a time referred to the official position of the sun rather than just an arbitrary hour.

Back in medieval and early modern England, people used mechanical clocks, sundials, and church bells to track the day. When specifying exact hours, they would say it was a certain hour of the clock.

Over time, as language naturally sped up for everyday conversation, people started clipping and shortening phrases to make them easier to say. The prepositional phrase was compressed into a single word. Just like we use an apostrophe in contractions like do not turning into don't, English speakers placed an apostrophe where the letters f and the whole word the were left out.

So, every time you check your watch and say it is three o'clock, you are secretly speaking a shortened version of old seventeenth-century English. It is a tiny linguistic fossil hidden right in plain sight in our daily schedules.