What is o in the "o'clock"? Is it an abbreviation?
Great question! "O'clock" is an abbreviation of "of the clock". This abbreviation originates from old times when people used different methods to tell time, like the sun. People back then had to differentiate between solar time, or time told from the sun, and time of the clock. So the phrase "of the clock" was used when referring to clocks, which has now been shortened to "o'clock".