Origins of Calender Names (days of the week and months) Names of days of the week come from the names of Greek, Roman and Norse gods. Sunday: Named after the Sun. Monday: Named after the Moon. Tuesday: Named after Mars, Roman god of war. Norse god Tiu or Tiwsday. Wednesday: Named after Mercury. Norse god Woden or Wodensday. Thursday: Named after Jupiter. Norse god Thor or Thorsday. Friday: Named after Venus. Norse god Fria or Friasday. Saturday: Named after Saturn. Also known as Saturni or Saturnisday. Names of the Months for the Gregorian calendar, are based on the ancient Roman calendar. The Roman calendar had 10 months: Martius, Aprilis, Maius, Junius, Quintilis, Sextilis, September, October, November, and December. The last six names were taken from the words for five, six, seven, eight, nine, and ten. The Gregorian calendar has 12 months, with the addition of January and Februray, where Februray takes into account calendar errors, thus we have leap day in this month, roughly every 4 years. January: named for Janus, the Roman god of beginnings and transitions. February: named for Februa, an ancient festival dedicated to ritual springtime cleaning and washing. March: named for Mars, the god of war. April: from the Latin work aspero, "to open", the opening buds of springtime. May: the Greek goddess Maia, who oversaw the growth of plants. June: the Greek goddess Juno, in latin juvenis - young people, which is why there is no school in June.. July: Originaly Quintilis latin for fifth, changed for Julias Caeser. August: Originaly Sextilis latin for sixth, changed for Augustus Caeser, grandnephew of Julius Caesar. Semptember: Latin for seventh, from the Roman calendar. October: Latin for eighth, from the Roman calendar. November: Latin for ninth, from the Roman calendar. December: Latin for tenth, from the Roman calendar.