Prima Primaria: For The Poor Souls In Purgatory

Purgatorial Societies

Pious associations or confraternities in the Catholic Church, which have as their purpose to assist in every possible way the poor souls in purgatory. The Catholic doctrine concerning purgatory, the condition of the poor souls after death, the communion of saints, and the satisfactory value of our good works form the basis of these associations, although they were called into life by pure Christian charity for one's neighbour which reaches beyond the grave. This brotherly love was the distinguishing mark of Christ's Church from the very beginning; the first Christian communities and the whole Church of the early centuries down to the time of the catacombs was one grand purgatorial society. The clearest evidence for this is supplied by the prayers for the dead in the oldest liturgies and breviary prayers, and by the earliest Christian inscriptions.

An excerpt from New Advent (here)

A Jesuit Ministry

The Sodality of Our Lady (also known as the Sodality of the Blessed Virgin Mary (in Latin, Congregationes seu sodalitates B. Mariæ Virginis) is a Roman Catholic Marian Society founded in 1563 in the Roman College of the Society of Jesus. On December 5, 1584, Pope Gregory XIII issued the Papal Bull "Omnipotentis Dei" commending this Sodality, enriching it with indulgences and establishing it as the Prima Primaria, that is, a mother Sodality which can communicate to other Sodalities affiliated with it the privileges and indulgences possessed by itself.
An excerpt from Wikipedia (here)

History of the Prima Primaria: Sodality of the Annunciation and Sts. Peter and Paul (here)

A book by Fr. Elder Mullan, S.J.