The name of March comes from Latin Martius, the first month of the earliest Roman calendar. It was named for Mars, the Roman god of war who was also regarded as a guardian of agriculture and an ancestor of the Roman people through his sons Romulus and Remus. His month Martius was the beginning of the season for both farming and warfare, 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. Martius remained the first month of the Roman calendar year perhaps as late as 153 BC, and several religious observances in the first half of the month were originally new year’s celebrations. Even in late antiquity, Roman mosaics picturing the months sometimes still placed March first.
More on: https://en.wikipedia.org/wiki/March