So I was in the shower a few days ago, musing over the fact that I can't, and have never been able to, quite get the order of the months right. This isn't the important part (besides, when I have to I can always count them out on my hands). The important bit of this revelation is that the months' numbers are off.
I realized that I could recall the order of the last few months with relative ease...why is that? I wondered absently. The answer hit me like a drop of water from the showerhead.
it's because they're already numbered.
September - from the roman septem- for seven.
October - from the roman octo- for eight.
November - from the roman novem- for nine.
December - from the roman decem- for ten.
I had never realized this before two days ago...and it blew my mind. What also blew my mind was that the numbers are apparently two off.
I found out later that this is because the roman calendar, from which these names are all derived, began in March instead of January. In fact, july and august used to have similarly prefixed names, but were later renamed for roman emperors (July for the month Julius Caesar was born, and August for Augustus).
Anyway, I found it interesting, but you don't have to.