Nonage reminds me of the Latin for weekend (not really, but the closest the Old Romans had for our concept): nundinae. Roman weeks where 9 days long. (If you're using a lunar calendar, you can divy the month up by four seven day weeks or three nine day weeks. It's complicated, usually by the fact that folks usually have a solar year to content with.) Anyway, the Romans divided up a month into Kalends (the first of the month), the Nones (the 5th or 7th of a month, but connected to nonus '9th'), and the Ides (the 13th or 15th, probably having to do with the fullmoon). It's all really complicated and obscure, and the Romans didn't even have names for the days of the week, they just used A through H, which gives us 8 days. 7, 8, 9? We get the seven day week from the Babylonians who divided the circle and the year into 360 degrees / days. They used a base-60 numbering system, sexagesimal, like the Maya. In keeping with ordinal numbers it should be octavage and septimage, but neither of these words occur. Nine was special, perhaps because it's the last digit in the decimal numbering system.