Interesting read this morning, apparently the original designers of the Roman calendar took after the decimal system and had ten months in a year. The last four were named by their numerical positions.

September (Latin-Spanish root: Siete; Sanskrit-Hindi cognate: Saat)
October(Ocho; Aath)
November(Nueve; Nav)
December(Diez; Das)

Around 700 BC they realized the accounting error. A new Calendar 2.0 version was released with two additional winter months Jan and Feb, but by now numerical misnomers at the end remained.

So it has been over 2000 years we live with this idiosyncrasy (and over 20 years of Windows start, stop, start again hoola hoops 3.1, 95, 98, 2000, 7, 8, 10...)!