In the Hebrew texts of the old testaments, God had but One Name which consisted of four Hebrew letters: Yud Hei Vav Hei or YHWH.
In KJV, this is often translated as the LORD or even Jehovah. Many people today know the tetragrammatron as Yahweh as well. As it is written, "You will not bring My name to vain." The Hebrew word for vain means "worthless" or "unused" meaning not to make His name unused and therefore forgotten. The true pronunciation is not entirely known because the ancients didn't write in vowels and the Pharisees (well, the Talmud) prohibited people from saying the Sacred Name (which ironically was in direct violation of the command not to make it unused). There is even a prophecy in Jeremiah which predicts the name of God becoming forgotten:
Jer 23:26 How long shall this be in the heart of the prophets that prophesy lies? yea, they are prophets of the deceit of their own heart;
Jer 23:27 Which think to cause my people to forget My Name by their dreams which they tell every man to his neighbor, as their fathers have forgotten my name for Baal.
Baal was an ancient pagan deity and in Hebrew even means "the lord." The LORD being the translation of YHWH was because the Jews replaced His Name with Adonai (meaning Lord or Master) in order to avoid saying the Name. Therefore, the texts ended up translating "LORD" instead of "YHWH." Even Messiah encouraged praying to the Name of God: "Father who is in heaven, hallowed be Your Name..."
The Hebrews had many titles for God but recognized His One True Name given to Moses. Other Hebrew titles include:
- Adonai
- El
- El Shaddai
- Eloah
- Elohim
- Eloheinu
- El Elyon
-Abba
And many other titles. There is also the factor of Him being the Lord of Spirits and the "Ruach HaKodesh" as it's known in Hebrew, or the Holy Spirit (known famously as the Holy Ghost) which was the Spirit of YHWH. There is also another attribute to Him called His Shekinah in Hebrew which means "Glory" referring to the Glory of God. When it comes to titles, attributes, and other factors associated to God, the Hebrews had many titles to express His dominion over the universe and to describe His nature.
The pronunciation of YHWH is forgotten but scholars and groups have opinions. The most accepted pronunciation amongst scholars and many Jews today is Yahweh. Smaller groups prefer the pronunciation of Yahuah but many Karaite Jews go with the translation of Yehovah or Yehowah, which is where KJV got Jehovah from. The pronunciation Yehovah/Yehowah is supported by the Masoretic Text which is the oldest Hebrew Tanakh (old testament) which had vowel placements in the Hebrew text.