I don't know for sure who invented it. What I can say is that the first commercially available drop away that I remember was the Muzzy Zero Effect rest. I had one and it worked well, though it was a nightmare to setup and get right. That was back in the late 90's I believe.
I think these were called opertune...circa mid-late 80s. Don't recall the maker. I also recall some rests that were not much more than a spring screwed into the riser.
