- Ancient Hebrew had no vowels. So the Name was rendered JHVH or YHWH (in Hebrew, of course, not Latin letters, so already we’re into approximating sounds)
- The Jews did not pronounce the Name of God (revealed to Moses). Whenever the Name appeared in the text, they substituted Adoni (“the Lord”)
- Both Jehovah (the older form) and Yahweh (more recent) are educated guesses as to how that Name might have been pronounced, had anyone pronounced it.
- Following the tradition of the Jews, many translations use the phrase “Lord God” in place of the Name (as distinct from just “God” which translates “Elohim” Some use LORD (all caps).
An interesting aside - in the Old Testament when God calls Abram and Sarai and changes their names, the change is the insertion of that ending syllable from God’s Name - they are “called by His Name,” as are we, in a way, when we are baptized into Christ.
Rome has recently (last June) reinstituted the prohibition of the pronounciation of the Name in the liturgy:
“By directive of the Holy Father, in accord with the Congregation for the Doctrine of the Faith, this congregation … deems it convenient to communicate to the bishops’ conferences … as regards the translation and the pronunciation, in a liturgical setting, of the divine name signified in the sacred Tetragrammaton,” said the letter signed by Cardinal Francis Arinze and Archbishop Malcolm Ranjith, congregation prefect and secretary, respectively.
The Tetragrammaton is YHWH, the four consonants of the ancient Hebrew name for God.
“As an expression of the infinite greatness and majesty of God, it was held to be unpronounceable and hence was replaced during the reading of sacred Scripture by means of the use of an alternate name: ‘Adonai,’ which means ‘Lord,’” the Vatican letter said. Similarly, Greek translations of the Bible used the word “Kyrios” and Latin scholars translated it to “Dominus”; both also mean Lord.
“Avoiding pronouncing the Tetragrammaton of the name of God on the part of the church has therefore its own grounds,” the letter said. “Apart from a motive of a purely philological order, there is also that of remaining faithful to the church’s tradition, from the beginning, that the sacred Tetragrammaton was never pronounced in the Christian context nor translated into any of the languages into which the Bible was translated.”
The two Vatican officials noted that “Liturgiam Authenticam,” the congregation’s 2001 document on liturgical translations, stated that “the name of almighty God expressed by the Hebrew Tetragrammaton and rendered in Latin by the word ‘Dominus,’ is to be rendered into any given vernacular by a word equivalent in meaning.”
“Notwithstanding such a clear norm, in recent years the practice has crept in of pronouncing the God of Israel’s proper name,” the letter said. “The practice of vocalizing it is met with both in the reading of biblical texts taken from the Lectionary as well as in prayers and hymns, and it occurs in diverse written and spoken forms,” including Yahweh, Jahweh and Yehovah.
Hope that helps