What is the X in X-mas?
fem. proper name, Biblical name of the wife of Aaron, from Late Latin Elisabeth, from Greek Eleisabeth, Eleisabet, from Hebrew Elishebha "God is an oath," the second element said by Klein to be related to shivah (fem. sheva) "seven," and to nishba "he swore," originally "he bound himself by (the sacred number) seven." Has never ranked lower than 26th in popularity among the names given to baby girls in the U.S. in any year since 1880, the oldest for which a reliable list is available.