March comes from Martius, and was named after Mars, the Roman god of war and an ancestor of the Roman people through his sons Romulus and Remus. It was the 1st month of the Roman year.

March

1. Festival of Mars.
2. Festival of Vediovis, an underworld version of Jupiter.

His month Martius was the beginning of the season for warfare,[1] and the festivals held in his honor during the month were mirrored by others in October, when the season for these activities came to a close.[2] Martius remained the first month of the Roman calendar year perhaps as late as 153 BC,[3] and several religious observances in the first half of the month were originally new year's celebrations.[4] Even in late antiquity, Roman mosaics picturing the months sometimes still placed March first.

March is the third month of the year in both the Julian and Gregorian calendars. It is the second of seven months to have a length of 31 days. In the Northern Hemisphere, the meteorological beginning of spring occurs on the first day of March. The March equinox on the 20 or 21 marks the astronomical beginning of spring in the Northern Hemisphere and the beginning of autumn in the Southern Hemisphere, where September is the seasonal equivalent of the Northern Hemisphere's March.