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 ten months long and included the following months—Martius, Aprilis, Maius, Junius, Quintilis, Sextilis, September, October, November, and December.
It was not until 45 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 to July and August in honour of Julius Caesar and Augustus Caesar,
Source: blog dictionary.
House sparrows on oats, September 1906. taken from
‘The Country Diary of an Edwardian Lady.’