>> The Arabic “Ilah” is the phrase for god, not “Allah” <<
Allah is a contraction of Al Ilah. I understand that it is specifically a grammatical contraction, not a portmonteau.
Also, not to make an argument of it, but I’m quite puzzled by your assertion that YHWH means “existing one.” Is that because you relate it to “I Am Who Am”? I’m told by Jewish friends that both the ‘J’ and the ‘V’ in ‘Jehovah’ are invalid transliterations. Hence, it’s “Netanyahu,” not “Netanjahu.” It’s also “Yeshua,” not “Joshua” which is a westernized name. Take it for what it’s worth. The point is that trying to fill in the missing vowels (all classical Hebrew words lack true vowels) is futile; All the letters “YHWH” are semi-vowels, making “YHWH” unpronounceable, and thus, impossible to take in vain. Trying to pronounce it yields the very ridiculous sounding, “Yahuwehuh,” and even that’s wrong because “yahu” can’t start a word and “wehuh” can’t end one.
The vowels in ‘Jahovah’ were simply the vowels in “Adonai,” which proper Jewish reference to God.
The use of JHVH or YHWH is simply a westerization of the Hebrew 'יהוה'. It has its origins in 'היה' (hayah) but contains the imperitive 'י'(ya) making it personal and specific.
The link below has a good exposition on it:
The use of "I AM 'היה' (hayah) WHO 'אשר' ('aher) I AM 'היה' (hayah)" is rather lengthy but does not mean 'existing one'. It simply means "I am who I am". The word 'היה' (hayah) is the Hebrew verb 'to be'.