TRIVIAL PURSUITS: Why do we say “o’clock” at the top of the hour?

Why do we say “o’clock” at the top of the hour?

“O’clock” is an abbreviation of “of the clock.”

As early as the 16th century, people who were asked for the time would clarify that they were referencing a clock in their answer. Clocks were not as prevalent then, and there were other methods for measuring the time.

For example, they would say it is three of the clock. This over time was contracted to three o’clock.