I just did some personal research on Gods name for my brother who is loosely attatched to the JW's through my parents. Most of the info. has already been stated, exept for the fact that the Jews would not pronounce the divine name because of a superstition they had due to a scripture in Exodus 20:7. And then only the high priest could say the name out loud once a year!!
The tetragrammaton is used 6,823 times in the OT. Somewhere between the 6th and 9th centuries, a Jewish religious group known as the Masoretes attatched vowells to the letters YHWH, thus creating Yaweh. As someone pointed out earlier in the post, around the 12th century translaters substituted a J for the Y as in latin, and a v for a w, and came up with Jehovah. In 1602, the spanish bible translation by Cipriano de Valera rendered the tetragrammaton thousands of times in the old testament as "Jehova", and later the King James used the name "Jehovah" just 7 times in the old testament.
Whats even more amazing, is how the WTS makes such a big deal over the importance of using the name Jehovah, (even to the point of critisizing some of praying to a false god if they dont use the name in their prayer.....this has personaly happened to me) and yet in one of thier own books, the "New World Translation of the Christian Greek Scriptures" they recognize that YAWEH is probably more correct than JEHOVAH. They say on Pg. 23 "While inclining to view the pronunciation "Yaweh" as the more correct way, we have retained the form "Jehovah" because of peoples familiarity with it since the 14th century."
I personaly agree with several others on this post. I became familiar with the name Jehovah as a child, and will continue to call on the Almighty by that name. Whether its Yaweh or whatever, he's still my Father, and i thats what i mostly call him. Truth seeker, i hope this helps.
Jim