December is the twelfth and last month of the year in the Julian and Gregorian Calendars. December got its name from the Latin word decem (meaning ten) because it was originally the tenth month of the year in the Roman calendar, which began in March. The winter days following December were not included as part of any month. Later, the months of January and February were created out of the monthless period and added to the beginning of the calendar, but December retained its name.
December from Très Riches Heures du duc de Berry