PSacramento,
Do you have a scholarly reference to prove that Jehovah is a combination of YHWH and Adonai?
I was always of the understanding that vowels were not used by the Hebrews in written form and that Jehovah's Witnesses accepted this pronunciation because of its dominant use by other Judeo/Christian groups throughout history.
It is in the dicitonary after all, as the Hebrew name for God. I highly doubt that Jehovah's Witnesses had anything to do with that. Meriam Webster usually has their shit together.