Bitt, I always thought that VisiCalc was the program that originated the term "Killer App." I don't know when it was described as such, but it looks like the first stable release was '83...
People in the restaurant industry have also used "app" for a long time to mean appetizer, which itself has gained some public traction.
I'm pretty sure I've never heard that, and would ignore it if I did. I don't know why it sounds so much dumber as an abbreviation for appetizer than it does for application, but it does to me...