In Old English, noon, or "12:00", "midday" was spelled non and it meant "the ninth hour since sunrise" (they used a different system of counting time in those days), or in other words, "3:00 pm", often the time of the monasterial midday prayers (which still exist today). This is when people in the old times considered the sun to be strongest, but as prayer times eventually moved, so did the definition, shifting to when the sun is highest. This is a shortening of the Latin phrase nona hora, or "ninth hour". We only really care about the nona part here, and that's a conjugation of nonus, also "ninth". This is from novem, "nine", from earlier noven, and, with a probable jaunt through Proto-Italic, ultimately from Proto-Indo-European hnewn, which may or may bot be in turn related to the PIE word for "new", newos. Usage of the word noon has also decreased since the nineteenth century. It's funny, looking back, how noon has roots in "nine" and "three" but none in "twelve" until very recently.
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