First at all, there is a new marketing video of God's name, clearly saying the name of God is Jehovah.
Link: https://tv.jw.org/#en/video/VODBible/docid-502014331_1_VIDEO
And then, there is the video with Geoffrey Jackson (GB) clearly saying that the original name of God is not known and the use of Jehovah is because of it is the most used variant in English.
Link: https://www.youtube.com/watch?v=Xwv_8oCVkJ8
So, something contradicts here, isn't it?
If the name of God is not know, why than all the GB hammering to use it.
Gorby