There were online stores that sold applications before Apple did so. What's wrong with calling them whatever we used to call them, before Apple started calling theirs "App Store"?
But "app" has been a genericized term since at the 1980s (See "Killer App"). And I'm not seeing how if "Foozit" is a generic term how you can copyright "Foozit Store" if the term is in fact describing a store which sells Foozits.