Updated: Sep 18, 2020
You can write the Father's holy name in any language and always capture the correct pronunciation, so long as you know what you're doing. When His name was written in Greek, by people who knew what they were doing, the three letters ΙΑΩ (iota, alpha, omega) were used. That's all you needed. The Father's name is not a Greek word, but you can spell His name with Greek letters. His name is also not an English word, but you can spell it with English/Latin letters.
Now the letter iota is normally an "E" vowel in Greek, but when the smooth breathing mark is placed before the letter iota, and iota is the initial letter of a word, and iota is followed immediately by a vowel, then iota is the consonant "y". This is a rule in Greek. I did not make up this rule.
Another rule in Greek is that when the vowel letter Α (alpha) "a" is followed by the vowel letter Ω (omega) "o" they do not combine to form one vowel (i.e. diphthong). Both alpha and omega must be pronounced separately with a voiceless glottal stop dividing them - i.e. "ah-oh".
So what you have in the historian Diodorus of Sicily, who was told by native Hebrew-speakers in ca. 60 BC how to pronounce the Father's name, is nothing short of incontrovertible proof that the holy name is just two syllables and these two syllables are pronounced "Ya-o". This is why I invented the Latin spelling convention YA'OH where the name is spelled in all caps and an apostrophe sign is used to keep the "a" vowel sound and the "o" vowel sound separate and distinct.
I know there is no apostrophe sign in ancient Hebrew. For those of you who think you need to tell me this, as if I don't already know this, you need to stop. You are missing the point and you are exposing your illiteracy.
I am simply using the apostrophe sign to facilitate the correct pronunciation of the holy name when it is spelled with Latin letters. This helps to ensure that people will not pronounce the Father's name like you would pronounce the name of the basketball celebrity Yao Ming. This name is just one syllable because the "a" and the "o" vowels are both combined into a diphthong, i.e. "Yow". But that is not how the Father's holy name is pronounced!
If you intend to mock the Father's name on social media by pronouncing it as if it is the same as "Yao" Ming's first name, because you are not willing to let go of one of those very recently made up fake names like Yahweh, Jehovah, Yahuah, Yahawah, etc., you do so to your own peril.
The good news is that you now know the correct way to say the Father's holy name. The bad news is that you now know the correct way to say the Father's holy name. Be very, very careful. This is not just a name.
His name is YA'OH. Always has been. Always will be.