Isaac = Yitzhak
Jerusalem = Yirusalem
Where does Josephus' 4th vowel come from?
This all seems like a quagmire to me. I mean divine...
I don't believe we know what the real YHWH would be, and if we could it still wouldn't matter.
I don't believe anyone left any conclusive clues, the original was lost to superstition.
And while Martini or anyone else of that time period may not have invented Jehovah, they certainly were the point of reinforcing it, an unknown as fact.