The Rosary and the Psalter of Mary
While an exact history of how the Rosary developed is not clear, Father Etienne Richer explained in “Mariology” that by the end of the 11th century, which would have been almost 100 years before St. Dominic, “a Marian devotion characterized by numerous Aves with rhythmic prostrations was already known and practiced in honor of the Virgin, first in honor of her joys, then in honor of her sorrows.” The name Rosary became associated with the practice.
In this same time period, Cistercian brothers and monks, who were not up to the task of memorizing the 150 Psalms that their order prayed each week, would recite 150 Pater Noster (Our Fathers). The laity soon copied this form of praying but substituted the Hail Mary for the Our Father. The name given to this devotion was the Psalter of Mary.