Origin of "Pay it forward"

I liked "Pay it forward" movie very much. It's an excellent nostalgic plot capable of getting you depressed; nevertheless, this time I am focused on an special idea that was shown at the beginning: Where that phrase came from?

This generation have internet, the greatest tool to share anything you might think of. This tool (and programming, for example) are at some scale really underestimated. Some entities are starting to show interest on people's ideas and creating tools to ease their sharing from people. This is good, but it should be global, maybe universal, and in reach of anyone capable to think, not to buy.

Then, the next step should be to filter ideas, and store but not reject them, because a silly idea after being better elaborated can become to a really good or important one.

Of course, Yin-Yang is always present, and ideas related to Money and Control are more attractive to powerful ones than Constant Improvement of People's Life. Grabbing and checking tons of ideas can even help to correct faults that Elite may not see.