It’s a word most of us say multiple times a day without thinking, but now, people are surprised to learn what it actually means.
The viral discussion began when a user posted a simple question on Threads: “What’s the meaning of ‘o’ in o’clock???”
Their query quickly caught fire, drawing a wide range of guesses from the internet.
People offered various interpretations, suggesting possibilities like ‘zero,’ ‘Omega,’ and even ‘oida,’ which is a Viennese term for ‘old person.’
For many online, this small linguistic revelation was mind-blowing. As one commenter put it: “Now I want to know its origin,” expressing the curiosity sparked by such a commonly used but little-understood term.
As the comment section filled with speculation, a few users pointed out a more historically grounded explanation: the ‘o’ is actually a shortened form of the word ‘of.’
One user elaborated: “At the invention of the clock, many people used the sundial, so to make the distinction, many people using the clock would state it’s ‘of the clock.’”
In other words, ‘3 o’clock’ originally meant ‘three of the clock,’ signifying the time shown specifically on a mechanical clock rather than estimated through sun positioning or other methods.
John Brown, posting under the handle @johnbrown2812, confirmed this theory: “The phrase ‘o’clock’ is a contraction of ‘of the clock,’ which was historically used to specify the time according to the clock.”
The Britannica Dictionary explains that the apostrophe in “o’clock” marks a contraction of the phrase “of the clock.”
“An apostrophe is used in o’clock because the word is a contraction of the phrase ‘of the clock,’” the dictionary notes.
Surprisingly, “o’clock” isn’t the only everyday expression with an unexpected origin.
According to Merriam-Webster, even the term “OK” has quirky historical roots. In the early 1800s, American humorists enjoyed playing with language, often using deliberately incorrect spellings for comedic effect.
For instance, “all right” became “O.W.” for “oll wright,” and “all correct” was transformed into “OK” as a shorthand for “oll korrect.”
So the next time you say, “It’s 5 o’clock,” remember—you’re echoing a phrase with centuries of linguistic evolution behind it.
