Catholics can and do use the name of God as represented by the Tetragrammaton, namely YHWH, usually translated as Yahweh as in the Jerusalem Bible. The latest instruction from the Holy Father is that God’s name is not to be uttered aloud in liturgical settings. Why not?
First, because that is the way it has generally been for liturgical settings—or for those who are not Catholics, that is the way it has always been handled in formal public acts of worship—since antiquity, dating back to worship in the Temple setting.
Considered too sacred to become used like an everyday common word or name, the Jews felt it was to be used sparingly, as something sacred or most holy. Why not use it frequently? Not only could such use make God’s name fall into the mundane, thought the Jews, but if not watched, this could lead to its being used for the profane.
This was likely not only the case in the oath-filled days of the Jews during the Hellenistic-Roman period, especially could this be the case in the cultures where heathen religions placed heavy emphasis on using a deity’s name at every opportunity and as frequently as possible. This practice was based on the belief that a worshipper would get a better hearing by a god this way, even to the point of forcing a god to grant their request because of repetitiously calling upon them by name.—Compare Matthew 6:7-8.
Sirach 23:9-10 reflects this ancient understanding: “Let not your mouth form the habit of swearing, or becoming too familiar with the Holy Name. Just as a slave that is constantly under scrutiny will not be without welts, so one who swears continually by the Holy Name will not remain free from sin.”
Originally used by all the Temple priests in pronouncing blessings, eventually it was only used by the High Priest during the liturgy of Yom Kippur (the Day of Atonement). Preservation of the Hebrew Scriptures by the early Christians and their subsequent writings showed that they too handled God’s Holy Name in this manner, by following the custom to read “Lord” instead of pronouncing YHWH aloud in worship as well in translating Holy Scripture. Christians also saw reflected in Christ the greatest revelation of the Holy Name of God—Yeshua (Jesus), which means “YHWH saves”—as well as Christ’s use of “I AM” as constantly quoted in John’s gospel account.
Viewing Jesus Christ as the True High Priest, and being truly Present in the gift and miracle of the Most Holy Eucharist, I AM is present and declaring Himself constantly in Catholic mentality, liturgically speaking. Because of this revelation of God’s Word, in the Eucharist and in the reading of Sacred Scripture during Mass, there is no reason for people present to utter what we believe Christ is already uttering by his True Presence in the Liturgy, even when that liturgical setting is something like the private reading of the Liturgy of the Hours. Why? Because all liturgy stems from and points to the Mass, where this Presence of I AM is proclaimed both sacramentally and by action of the priest and public during formal worship.
However, this does not mean that Catholics cannot utter the Holy Name. Outside of a liturgical setting it can be read aloud. It occurs in our Bible translations, if not in the text itself at least in the footnotes. It can also be found in our catechesis materials. And it is a part of history itself. But Catholics at large seem to be returning to this custom even in their private lives of showing reverence for God’s name this way by leaving it unpronounced and replacing it with something like “Lord” or “God,” even when coming across it in such publications.
After the 1960s when the Mass became translated into the everyday language of people, like English, some use of the Holy Name crept in that was not proper to the liturgical setting. Because Mass texts in all languages are currently being revised to more precisely match with the official Latin version, this misapplication of the Holy Name was given the attention necessary to readjust any who had forgotten to follow the ancient standard.