The rosary was originally called the Psalter of the Blessed Virgin Mary because Our Lady is venerated by the angelic greeting (the Hail Mary) repeated one hundred fifty times, corresponding to the number of the Davidic Psalter, and by the Lord’s Prayer before each decade. Superimposed on these prayers are certain meditations showing forth the entire life of Our Lord Jesus Christ, thus completing the method of prayer devised by the Fathers of the Holy Roman Church. In this we see that the rosary actually has its origin partly in the Divine Office, the official prayer of the Church, in which all 150 Psalms are recited/chanted in the course of each week.

The 150 Davidic Psalms (the Psalter of David) have always been prayed by Old Testament Israel , Jews, and Christians for personal prayer, communal prayer, lamentations, praise, thanksgiving, and, in the case of Christians, to demonstrate the fulfillment of prophecy.

They came to form a large part of the Divine Office sung at the various canonical hours by religious. Lay people who didn’t have copies of Scripture or the Breviary and lay people and religious who were illiterate would substitute 150 Pater Nosters (Our Fathers) or Aves (Hail Marys) in place of the 150 Psalms they could not read.

The prayers were originally counted by transferring pebbles from one bag to another, but soon enough Christians began to tie a rope with knots on which to count. This evolved further into using beads or pieces of wood in place of the knots, and this soon came to be called the “Psalter of the Laity.” Around the end of the first millennium, Rosaries contained the present five decades (sets of ten beads), with the Ave beads shaped like white lilies for the purity of the Virgin, and the Pater beads shaped like red roses for the wounds and Passion of Christ.

St. Dominic de Guzman popularized the Marian Psalter in the form we have it today (150 Aves with a Pater after each 10) when Our Lady encouraged him to pray it that way in response to the Albigensian heresy. So associated with the Rosary is St. Dominic that the Rosary is often called the “Dominican Rosary.”

Our Lady also appeared to the children at Fatima and asked that the Rosary be prayed daily, including the “Fatima Prayer,” as part of what must be done in order to prevent Russia from spreading its errors throughout the world (the other things being the faithful wearing of the Brown Scapular, the First Five Saturdays Devotion, acts of reparation and sacrifice, and the Consecration of Russia to her Immaculate Heart by the Pope and all the Bishops in union with him. This last has not been done).

The Rosary, thus, has always been a weapon against heresy and trouble; in fact, the October 7, 1571 victory of Christendom over Islamic warriors at the Battle of Lepanto — the first naval victory against the infidels — was attributed directly to the Rosaries prayed by the faithful.

While non-Catholics see the Rosary as a mindless chant, what they do not understand is that the Rosary is a meditation on the lives of Mary and Jesus. Each decade (each set of 10 Ave beads in the circular part of the Rosary beads) represents a single Mystery in their lives, and as the prayers are prayed, we contemplate that particular Mystery. There are 3 sets of 5 Mysteries — the Joyful, Sorrowful, and Glorious Mysteries.

One set of Mysteries is traditionally prayed on different days of the week, and one who prays a single set (i.e., 50 Aves) can be said to have “prayed the Rosary,” but, literally, a complete Psalter consists of all 15 Mysteries (150 Aves, going around the beads three times). The typical way of Rosary-praying — i.e., praying a third of a Rosary — is more accurately, but uncommonly, called praying a “chaplet.” (Note that there are many, many different kinds of chaplets — some to Jesus, some to the Holy Ghost, some to Mary and the other Saints, etc. — each with different arrangements of prayers and many having their own style of beads). Like the Mass, what you take emotionally from the Rosary is what you bring to it, but in any case, emotional highs aren’t the point of prayer. Prayer is for the glory of God.