What is the X in X-mas?
eighth month, 1097, from Latin Augustus (mensis), sixth month of the later Roman calendar, renamed from Sextilis in 8 B.C.E. to honor emperor Augustus Caesar, literally "Venerable Caesar" (see august (adj.)). In England, the name replaced native Weodmonað "weed month."
eighth month of the Gregorian calendar. It was named for the first Roman emperor, Augustus Caesar, in 8 BCE. Its original name was Sextilus, Latin for "sixth month," indicating its position in the early Roman calendar.