Is JEHOVAH God's name?
No. But it's a pretty good guess.
The word is a Latin-based hybrid of the vocalization of the Hebrew tetragrammaton (YHWH) as the proper name of the Hebrew god. Basically, Latin letters were used to replace Hebrew letters, and because the Hebrew alphabet has no vowels, the vowels were just assumed. "Jehovah" as a word didn't exist until the 1500s. Since then it has been somewhat debated because of the bastard nature of translation (letter-for-letter translation) and the assumption of the vowels. But it was widely accepted by the prodestants who included it in thier bible... which is how the JW's got a hold of it.
SIDE NOTE: To use ONLY the tetragrammaton for the name of god is a little disrepectful. The Hebrew god actually has many names depending on the aspects of YHWH (Orthodox Jews would argue this, I think). So, unless one uses ALL the names given and understand the meaning of each one, there is no gravity given to YHWH as a god... he is over-simplified in presentation.
It would be like trying to encompass all the effect that William Shakespeare has had on world literature humanity by just simply calling him "Willy".