Good stuff.  I am a Robert Heinlein fan...and I have heard from others that he is the originator of the term "Pay it Forward" in his book, "Between Planets".  The book was published in the early 1950s.  I have the book next to me so I will try to find the quote in it.  But I am not positive if he is the one who came up with it or just the one who made it more widespread.  I know that he very much followed this mantra in his own personal life.

Also, there is a Heinlein society that essentially engages in charitable acts of "paying it forward", based on the author. 

Here you go...from the 1951 Between Planets by Heinlein (with emphasis by me).  Don (Harvey) is the protagonist in the story:

His pride said no; his stomach said YES! Don took it and said, "Uh, thanks! That's awfully kind of you. I'll pay it back, first chance." 

"Instead, pay it forward to some other brother who needs it."

 Thanks Cubwin;)