It’s a well-known bit of trivia that the names of September through December are derived from numbers, and that they’re the wrong numbers with our calendar laid out as it is now. But before reading The Name of the Rose, whose chapters are named according to the canonical hours, it hadn’t occurred to me that the word “noon” is also a number that was mislaid somehow: it comes from the Latin nona hora, “ninth hour.”
The Romans’ days were divided into twelve hours of darkness and twelve hours of light (meaning that a daylight hour was longer than a night hour during the summer, and vice versa during the winter). The ninth hour began some time between what we would call 1:45 and 2:45 PM.
“Nona hora” was adapted into “nones,” the name of one of the hours at which some Christians were required to pray, and this in turn became our “noon.” The term had shifted into its current meaning by the 14th century, says the Online Etymology Dictionary,1 although the reason for the change is unclear. (I love the suggestion that monks gradually pushed nones back by almost three hours so they could end their fasts earlier!)