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early 15c., in reference to the Roman calendar, "ninth day (by inclusive reckoning) before the ides of each month" (7th of March, May, July, October, 5th of other months), from Latin nonæ (accusative nonas), fem. plural of nonus "ninth." Ecclesiastical sense of "daily office said originally at the ninth hour of the day" is from 1709; originally fixed at ninth hour from sunrise, hence about 3 p.m. (now usually somewhat earlier), from Latin nona (hora) "ninth (hour)," from fem. plural of nonus "ninth," contracted from *novenos, from novem "nine" (see nine). Also used in a sense of "midday" (see noon).
Old English nan (pron.) "not one, not any," from ne "not" (see no) + an "one" (see one). Cognate with Old Saxon, Middle Low German nen, Old Norse neinn, Middle Dutch, Dutch neen, Old High German, German nein "no," and analogous to Latin non- (see non-). As an adverb from c.1200. As an adjective, since c.1600 reduced to no except in a few archaic phrases, especially before vowels, such as none other, none the worse.