I love that analogy. No, you're not going to personally save the world by reducing your carbon footprint. But you know what you are going to be? One leaf on a tree in a forest, making that little bit more oxygen that helps collectively make the world a better place.
And that's worth doing. Especially if you can encourage other people to be leaves too.
We, well those of us in environmental activist roles anyway, were using the term regularly and as part of our public messaging in the mid-90's.
Bill Rees came up with the term at UBC a few years earlier and it was catching fire, but environmentalism is poorly funded so the messages spread slowly. Oil companies saw a grift opportunity and used it as a deflection strategy a few years later. They just got there first, and by throwing gobs of marketing money at it, controlled the narrative.
The message was getting out, but not at hypercapitalist rates. BP oiligarchs don't deserve credit for popularizing the term. Rees does, he did more than just coin it, he worked with us to make sure we built tools to understand it.