Earlier quoted context omitted.
at the risk of telling you what you already know... programmes on the mac have the extension .app; it's roughly equivalent to .exe in Windows (except it's not a binary, more like a .jar). When the iPhone started, I guess 'App' was the natural name for them, and thus App Store came naturally as well. Now it's come to the mac, it's makes even more sense, because it's back where it (Apps) started
Minor historical note: the .app extension for application bundles is a holdover from NeXTSTEP. I don't think that has anything to do with the usage of "app" on the iPhone, and I think the Mac App Store is branded that way for similarity with the iPhone store.
Really? Why not? The iPhone is, after all, running a decedent of the NeXT codebase too.