Devotion to our Blessed Mother under this title is almost five centuries old in the order. During the reign of Pope Paul II (1464-1471) a picture of the Blessed Mother appeared miraculously on the wall of the Augustinian church in Genezzano, Italy. A shrine was erected to our Blessed Mother under the title "Mother of Good Counsel". The shrine soon became famous because of the report of special graces and miracles. It was visited not only by persons from the cities close to Genezzano, but by pilgrims from places a great distance away.

A Pious Union in honor of the Mother of Good Counsel was instituted. It was approved and confirmed by Pope Benedict XIV. He and other Popes granted many indulgences to members of the Union. Pope Pius VI granted to members of the Augustinian Order a special Mass and Office in honor of the Mother of Good Counsel.

Pope Leo XIII ordered that the invocation, "Mother of Good Counsel, pray for us", should be added to the Litany of the Blessed Mother.

Reference: http://campus.udayton.edu/mary/resources/music/OLGoodCounsel3.html