"Sacred Scripture contains no text concerning the event commemorated in today's liturgy. For something of a historical background one may consult the apocryphal works, particularly the Protoevangel of St. James (ch. 4:1ff). After an angel had revealed her pregnancy, Anna is said to have vowed her future child Mary to the Lord. Soon after birth the infant was brought to the sacred precincts at which only the best of Israel's daughters were admitted. At the age of three she was transferred to the temple proper (7:2). According to legend, here she was reared like a dove and received her nourishment from the hand of an angel (8:1).

"In the East, where the feast, celebrated since the eighth century, is kept as a public holiday, it bears the name, 'The Entrance of the Mother of God into the Temple'. It was introduced at Rome by a Cypriotic legate to the papal court of Avignon in 1371. In 1472, Sixtus IV extended its observance to the whole Church. Abolished by Pius V, it was reintroduced some years later (1585)."

http://www.catholicculture.org/culture/liturgicalyear/calendar/day.cfm?date=2013-11-21