Thanks for watching my talk! I actually misquoted Tom and mentioned “adjacent possibilities” instead of “the adjacent possible” 
… I had only really heard Tom talk about this concept, and hadn’t taken the time to understand it myself.
I think you’re exactly right about the origin of the term. There’s a book called " “Where Good Ideas Come From” by Steven Johnson where he expands on this, there’s a Blinklist summary of the key ideas.