“Yehovah”, or “Jehovah”, which the King James version of the Bible uses as the name for God, is actually not a word. It is the consonants of one word with the vowels of another. Here is why.
The Hebrew Bible was originally written with all consonants. The vowels were added by the Masoretes in the Middle Ages to help with pronunciation. The name of God is composed of the consonants “YHVH” (or YHWH). If you look at the Name in a Hebrew Bible, it looks like it should be pronounced “Yehovah”. But this is misleading.
It’s almost certain that the first syllable is pronounced “Yah”, because this short form of the Name is used often in the Hebrew Scripture (e.g. Psalm 122:4). This short form is also the last syllable of the word “Hallelu-Yah”, which is an imperative meaning “Praise Yah”.
It’s also well-known that Jews in general did not say the name of God for fear of taking his name in vain, one of the prohibitions in the Ten Commandments. They would typically substitute another word, often the word “Adonai”, which means “Lord”. Many modern Bible translations use the word “LORD” where the Hebrew has “YHVH” for this very reason. It’s also clear that Jesus followed this tradition, as there is no record in the New Testament of him pronouncing God’s Name.
When the Masoretes added vowels to the Hebrew Bible in the Middle Ages, they added the vowels of “Adonai” to the divine Name to remind people to pronounce it this way. We know this because when the Name occurs alongside the word “Adonai”, they insert the vowels of the word “Elohim”, the word for “God”. This occurs a lot in the book of Ezekiel (e.g. 3:27; 4:14; 5:5). If pronounced as written, this comes out sounding like “Yehovee”.
Some people (with a limited knowledge of Hebrew) complain that the first vowel of “Adonai” is different from the first vowel added to the divine Name. This seems to be true, but really isn’t. The first vowel of “Adonai” is a compound vowel, a shewa and a qamats, known as a “hateph qamats”. This is a very short form of an ‘A’ vowel, which is why it’s transliterated with an ‘A’ in “Adonai”. But the compound vowels, such as the hateph qamats, only occur under a few consonants (gutterals), mainly Alef and Ayin. Under normal letters, such as Yodh, this vowel becomes a vocal shewa, which is transliterated with an ‘E’. That’s why the word that looks like “Yehovah” has an ‘E’ in the first syllable; it’s a shewa representing the hateph qamats in “Adonai”.
A similar thing, though not as visible, happens with the first vowel of “Elohim”, a hateph seghol, which is transliterated with an ‘E’. When it becomes a shewa in the divine Name, it remains an ‘E’ in English. The shewa in the divine Name and the compound vowels in “Adonai” and “Elohim” are really the same class of vowels, not different. It’s just that the shewa is required under a Yodh.
Although we are pretty sure that the first syllable of the divine Name is “Yah”, the next syllable is anybody’s guess. Some think that the Name is “Yahweh”, but that’s just a guess. Many names in the Bible had “Yah” as part of their name, such as Isaiah and Jeremiah. If we today want to use the Name of God, we should either use the short form, “Yah”, or substitute another word such as “Adonai” or “HaShem” (“the name”). It’s totally inappropriate to use “Jehovah” or “Yehovah” to refer to God.