Chris Jackson of The Remnant has provided another excellent article on the reasons why the Church adopted the Latin language in her liturgy, decrees, and official communications. The article was written in 1919 by Father John Francis Sullivan and it is found in chapter XIX in the book, The Externals of the Catholic Church.
Before I post the article I want to note a few simple points that will complement the article.
First, we should know that the Apostles all spoke Greek in addition to their native Aramaic. It was the language of education and business. In Galilee (Galilee of the Gentiles as it was known in Palestine) a Jew had to know Greek if he wanted to talk to a gentile. Perhaps Our Lord Himself spoke Greek with the Roman centurion and Pilate. In the synagogues the Jews read from the Hebrew translation of the Greek translation (the Septuagint) of the Old Testament. Second, all of the New Testament — with the exception of Saint Matthew’s original Gospel which was written in Aramaic — was inspired in Greek. Third, when Saint Peter came to Rome the Jews residing there spoke Greek, the whole Mediterranean world did. Saint Peter offered Mass in Greek. Around his tomb, deep in the catacombs under Vatican hill (beneath Saint Peter’s main altar), the faithful who were buried all around the Apostle had “Peter pray for us” written in Greek on their own tombs. Fourth, the Roman Latin Rite grew slowly out of Itala Latin which was spoken by the gentile converts in Italy and North Africa and used in the liturgy sometime after Greek fell into desuetude in the West. Classical Latin (Ciceronian) was not used in the liturgy, but was used by the well-educated fathers, such as Tertullian, Saint Cyprian, Saint Hilary of Poitiers, Saint Ambrose, and Saint Augustine, in their writings. By the fourth century, Itala Latin, which was rather fluid, dominated in most of Italy and North Africa. Enter Saint Jerome (d. 420). His Latin Vulgate translation of the Bible facilitated the birth of what developed into “ecclesiastical,” Church Latin. Many Greek words found their way into Church Latin on account of their theological and scriptural importance. Ecclesia (church) is only one such word — there was no word in Latin adequate enough to convey such a Greek concept. By the sixth century, Latin became the standard for the Roman liturgy, as we see in the Leonine Sacramentary and later the Gelasian. By the time of Gregory the Great (d. 604) the Latin Canon of the Mass was fixed (canonized) with the addition of a number of Roman martyrs in the Memoriam and the Nobis Quoque Peccatoribus. The Roman Canon remained untouched for nearly fourteen hundred years.
THE official language of our Church is Latin. It is used in her services in the greater part of the world. It is employed in nearly all the business correspondence of the Holy See. Encyclicals and briefs of Popes, decrees of General Councils, decisions of the Roman Congregations, acts of national and provincials councils, synodal regulations of dioceses – all these are expressed in the ancient tongue of Rome.
The works of many of the great Fathers of the Church after the first three centuries and the countless tomes that treat of theology, Scripture, Church law and liturgy, all use the same majestic language. Full article is here.