For many, the month of September signals the end of summer, the beginning of autumn, and the start of a new school year. With respect to the calendar, September marks the beginning of the series of months named after their numerical position in the year.

Strangely enough, however, September is not named after the number nine.

What does September mean?

September comes from the Latin root septem-, meaning “seven,” because in the original Roman republican calendar September was the seventh month of the year rather than the ninth. The Roman calendar was only 10 months long and included the following months: Martius, Aprilis, Maius, Junius, Quintilis, Sextilis, September, October, November, and December.

The last six months were assigned names according to their ordinal numbers. Quintilis is the fifth month, Sextilis is the sixth month, and so on.

When did the calendar change?

It wasn’t until 46 bc, when Julius Caesar introduced the Julian calendar (named after Caesar, himself), that the year grew to include two more months, January and February. Quintilis and Sextilis were later renamed July and August in honor of Julius Caesar and Augustus Caesar, but despite repeated attempts to change them, the names for September, October, November, and December not only stuck, but spread to other languages as well.

The strangeness of calling the ninth month “Seventh Month” didn’t seem to bother Old English speakers. September replaced the Old English forms Hāligmōnað and Hærfestmōnað, which mean “harvest month” in modern English.

If the Roman senate had gotten their way, we might now be calling September Tiberius or Antoninus, after two Roman Emperors. Or we might have ended up calling September Augustus as followers of the Emperor Commodus hoped, or Germanicus, as Emperor Domitian wanted.

Would these names have been any better than calling the ninth month September?

Those ancient Romans really enjoyed playing with the calendar, like creating “Mercedonius,” the annoying month that used to exist (sometimes).