What does the "O" in "o'clock" really mean?

The term "o'clock" is a staple in the English language, used by millions daily to express time. Yet, the true meaning behind the "o" in "o'clock" has recently sparked curiosity online, leading many to explore its historical roots.

A question raised on the social media platform Threads asked, "What’s the meaning of ‘O’ in o’clock?" This query prompted a variety of responses, with users suggesting that the "o" might stand for "zero," "Omega," or even "oida," a Viennese term for "old person." However, the real answer is steeped in history.

The "o" in "o'clock" is actually a contraction of the phrase "of the clock." In earlier times, when clocks were still a relatively new invention, people would specify the time by saying it was "3 of the clock" to differentiate it from other time-telling methods like sundials. Over time, this phrase was shortened to "3 o'clock," with "of the" becoming simply "o'."


This explanation is supported by authoritative sources such as the Britannica Dictionary, which notes that the apostrophe in "o'clock" represents the contraction of "of the clock."

Interestingly, the use of "o" in this context is not unique. For example, the term "OK" or "okay" also has an unusual origin. According to Merriam-Webster, in the 1820s and 1830s, humorists often deliberately misspelled words to create a rustic, uneducated persona. "All correct" was humorously transformed into "oll korrect," which was then abbreviated to "OK," a term that has persisted in the English language to this day.