Today, May25 is the Feast of the Body and Blood of Christ. remember in the past it was always called Corpus Christi (which means the same thing). Why did they drop the latin?
Strictly speaking, the name of the past feast was only “The Most Holy Body of Christ” (Ssmi. Corporis Christi, in popular usage Corpus Christi). There was no mention of the Blood in the title, although the texts of the Mass and Office(i.e. the Liturgy of the Hours) made reference to the Blood.
The change in title came about due to the feast of the Precious Blood. The feats of the Precious Blood arose as part of what some call the ‘devotional’ feasts - as a devotion to the Sacred Humanity of Christ. It formed part of the group of “Passion feasts”, so called, that were celebrated on the Fridays of Lent in many places - the Lance, the Burial Cloth, Crown of Thorns, Five Wounds. These feasts were on local calendars and at the ebginning of the 20th century, were observed in most places.
In 1849, Pius IX declared the first Sunday of July as a feast of the Precious Blood to be observed universally. He did not remove the Friday Lenten feast which continued on many local calendars
In the calendar reform of St. Pius X, the Precious Blood was moved to July 1, and in accordance with the mindset of the liturgical pronouncements of the day, many dioceses and orders dropped the ‘Passion’ feasts. These were retained, though, as before, at the back of the missal in an appendix titled ‘Pro Aliquibus Locis’ - for various places.
In 1961, all such feasts of devotion were dropped from this appendix unless their retention was requested (with a good reason) by the order/congregation or diocese which had a special connection to it. The Lenten feast of the Precious Blood thus ceased to be observed.
However, John XXIII was devoted to the Precious Blood. He added “Blessed be his Most Precious Blood” to the Divine Praises, approved the Litany of the Precious Blood, raised the rank of the feast of July 1 and encouraged the devotion.
At the end of the 60’s, the thorough revamping of the Universal calendar was taking place, and it was decided that all ‘devotional’ feasts, should, as far as possible, be removed, or reduced in rank. The Precious Blood was therefore excised from the calendar for July 1. But soon there were petitions pouring in from bishops and places requesting that it be retained. The *Concilium *did not wish to put the feast back, so they merely added the title “and Blood” to the feast of the Eucharist so that the title reads, as now “The Most Holy Body and Blood of Christ (of the Lord)”.
That is why it may not be called “Corpus Christi” any longer, because now the title includes a reference to the Blood and people may not know the new Latin title. In my parish however, everyone still calls it “Corpus Christi”.
The Precious Blood, incidentally, was later retained as a Votive Mass in the missal. Strictly speaking though, the two devotions are not exactly compatible, as can be seen from the history of the Precious Blood. One considers the Blood under the general idea of the Eucharist and is focused on that, while the other has a wider scope considering the Blood under the general idea of the redemption