Some days ago Blondie gave me a hint on how Rutherford came up with "this idea":
"Brother Rutherford told me himself that he woke up one night when he was preparing for that convention and he said, `What in the world did I suggest an international convention for when I have no special speech or message for them? Why bring them all here? And then he began to think about it, and Isaiah 43 came to his mind. He got up at two oclock in the morning and wrote in short-hand, at his own desk, an outline of the discourse he was going to give about the Kingdom, the hope of the world, and about the new name. And all that was uttered by him at that time was prepared that night, or that morning at two oclock. And [there is] no doubt in my mind - not then nor now - that the Lord guided him in that, and that is the name Jehovah wants us to bear and were very happy and very glad to have it. "
( 1975 Yearbook of Jehovah's Witnesses , quoting A.H. Macmillan on the invention of the name Jehovah's witnesses, p. 151)