When asked about it, Jesus said the greatest commandment was, “Hear, Israel, the Lord is God, the Lord alone.”
I have heard that the Hebrew for that was, “Shma, Israel, Adonai Elohim, Adonai
There, the Hebrew “Shma” is much stronger than our English “hear.” It meant, “Be quiet and listen.”
Now, for the Jews, God’s personal name was Yahweh, but we meet with two difficulties there.
For one thing, when writing in Hebrew they left out letters for the vowels, depending on the reader knowing what fit in there. That being so, for Yahweh, they wrote only the letters YHWH.
The second difficulty they made for us there was that for fear of breaking the commandment against taking the Lord’s name in vain, when they came to the written YHWH, they substituted the other name for “Lord’ which was “Adonai.”
Since the name Yahweh was never pronounced, people began adding other vowel sounds to make uo the non name of Jehova.