JHVH with the vowels from Adonai, you get "Jahovah
No. You don't. jEhOvAh vs. AdOnAI. :-P
Josephus said that it is pronounced according to it's letters/vowels.
It has YHWH, and the word for Judah has YHWDH but pronounced
YEHOWDAH you take the D off and you're left with YEHOWAH
And that's where Martin the Catholic Monk gets the pronunciation in
Latin IEHOVAH, (YEHHOWAH), the Masoretes used the right vowels, an EH to start and an AH at the end.
From Yehowah you can derive Yah, Yahu and Yeho combined names of Biblical characters. Whenever a noun is in a construct state the first vowel gets shortened to a schewa.
The Adonay fallacy is something that gets repeated by folks who hear it and pass it on. The Yahweh pronunciation is a "scholarly" construct that is just not supported in the historical record.