In Hebrew
the name of God is spelled YHWH. Since ancient Hebrew had no written
vowels, it is uncertain how the name was pronounced originally, but
there are records of the name in Greek, which
did have written vowels. These records indicate that in all likelihood the name should be pronounced "Yahweh."
Shortly before the first century A.D., it became common for Jews to
avoid saying the divine name for fear of misusing it and breaking the
second commandment ("You shall not take the name of the Lord, your God,
in vain," Dt 5:11). Whenever they read Scripture aloud and encountered
the divine name, they substituted another Hebrew word, "Adonai" (which
means "Lord" or "my Lord"), in its place.
Eventually Hebrew developed written vowels, which appeared as small
marks called vowel points and were placed above and below the consonants
of a word. In the sixth or seventh century some Jews began to place the
vowel points for "Adonai" over the consonants for "Yahweh" to remind
the reader of Scripture to say "Adonai" whenever he read "Yahweh."