Most Christians know that in English translations of the Bible, the capitalised “LORD” stands in for the Tetragrammaton, the divine name, YHWH. Actually, the Hebrew people regularly pronounced the name until the destruction of the first Temple in 586 B.C. This is seen in the Lachish Letters, which were written before the Temple’s destruction, and contain the Tetragrammaton.
After the destruction of the Temple, and the end of the exile, Jews from about the third century BC began using the substitute Hebrew word for master or Lord, Adonai, when they read YHWH. Later Masoretic scribes took the vowels from Adonai, and placed them within the divine name to remind readers to reverently say “Adonai” instead of the divine name. This ended up looking like YeHoWaH to later medieval Christian scholars, who did not understand what this meant, and introduced the hybrid name “Jehovah”.
Later Jews took this even further, using Ha-Shem (“the Name”) to refer to God. For many, it is impiety to attempt to pronounce the name of God, as if it is a mystery lost in time. But the Jewish writer Louis Hartman writes in the Encyclopaedia Judaica:
“The true pronunciation of the name YHWH was never lost. Several early Greek writers of the Christian Church testify that the name was pronounced “Yahweh.” This is confirmed, at least for the vowel of the first syllable of the name, by the shorter form Yah, which is sometimes used in poetry (e.g., Ex. 15:2) and the -yahu or -yah that serves as the final syllable in very many Hebrew names.”
What then? While the name of God should be respected, it is hard to believe it was revealed so as to remain unpronounced. On good evidence, we know ancient Israelites pronounced it as Yahweh.
Because of changes in the Hebrew language too technical to go into here, we now pronounce with a v much of what was then pronounced with the w sound. (That is, the letter vav in modern Hebrew was a waw in ancient Hebrew). For that reason, today we speak of the Levites, not the Lewites; King David and not King Dawid. To be consistent, today we would pronounce the Tetragrammaton as Yahveh.