The first known Marian invocation goes back to the third century and begins with the words: "We fly to thy patronage (Sub tuum praesidium), O holy Mother of God...". However, since the 14th century the most common prayer among Christians has been the "Hail Mary".
By repeating the first words the angel addressed to Mary, it leads the faithful to contemplate the mystery of the Incarnation. The Latin word "Ave" translates the Greek word "Chaire": it is an invitation to joy and could be translated "Rejoice". The Eastern hymn "Akathistos" repeatedly stresses this "rejoice". In the "Hail Mary" the Blessed Virgin is called "full of grace" and is thus recognized for the perfection and beauty of her soul.
(POPE JOHN PAUL II, GENERAL AUDIENCE, Wednesday, 5 November 1997)