Originally Posted By: DoubleWasp
I was going to start a thread about what exactly "o'clock" is supposed to mean, but I guess I'll just forget it.
This is where "o'clock" came from:
"To distinguish the fact that one was referencing a clock's time, rather than something like a sundial, as early as the fourteenth century one would say something like, “It is six of the clock,” which later got slurred down to “six o'clock” sometime around the sixteenth or seventeenth centuries."