"Origins of words" by Susie Dent, Countdown 22/02/18 (time: o'clock, am, pm, noon)

I had a tweet from Janice Scott, who asked why we started telling time in terms of o'clock and when we started doing it. And it's nice question. The original form of the expression, you probably won't be surprised to know, was of the clock and it goes back centuries to at least Chaucer's Day, so you'll find of the clock in the 14th century. Right up until Victorian times, you might still find a formal invintation being issued that eould give a certain time to arrive of the clock. English speakers tried lots and lots of different forms over the years. You might have heard two of clock, two a'clock, three at clock or simply three clock, which I quite like, but our standard form, o'clock, is first recorded in about the 18th century. And the use of 'o to mean of was well known, particularly at that time, and had been around ainse Middle Ages, so you'll find it in things like will-'o-the-wisp, jack-'o-lantern, that kind of thing, so it wasn't a greate push to come up with two o'clock, for example. And like two o'clock, most of the forms have been used with whole numbers only, so you won't find three thirty o'clock, we've never used that. But indication of morning and afternoon was a little bit more complicated, s othe expression was extended further. So it would be six o'clock at night, nine o'clock in the morning, and we still use that sometimes, but of course now we've graduated to am and pm. And am's short from ante meridiem, and pm's short from post meridiem - before and after noon. They were introduced the second half of the 18th century, so again they've been around for quite some time, they've made things a lot easier. But just while we're on time, it's worth just reminding that noon actually comes from the Latin, the Roman nona hora, which meant the ninth hour. Which seems a litte bit confusing, really, but they started counting not from midnight but from the hours of daylight, so nona hora was the ninth hour from daylight. So their noon was around three o'clock in the afternoon. And that nona, meaning ninth, has absolutely no relevance today, but it's just a bit of relic from ancient times, from ancient Roman times, that we still refer to nine when we talk about noon.