After summer we are now heading towards the end of the year. The period called as autumn, or fall, depending where you come from. In agricultural times also known as the harvest season. Despite their difference they all have the connotation of the passing towards the end. Where autumn derives from Etruscan autu-, fall is simply the fall of the leaves, or the year (contrast to the spring of the year). In Finnish September is 'Syyskuu', literally the 'autumn month'.
Officially autumn started on Monday, 23rd which marks the September equinox. And lasts until winter solstice when the winter finally breaks in. Another way to define autumn is by thermal season in which the autumn starts when there are 5 or more consecutive days with average temperature below +10 degrees Celsius.
September comes from the Latin 'septem' meaning seven. While being ninth month today, it used to be the seventh month during ancient Roman times. According to some legends it got demoted to ninth month after Julius Caesar inserted July and August to the calendar to honor himself and the first roman emperor Augustus. In truth the months January and February were already added a couple of hundred years before the Julian reform and the seventh and eighth months (Quintilis and Sextilis) were later named after those two emperors.