Okay, I did some research like you suggested.
There may be some anecdotal use of the term "app" before the iPhone (none of which I can easily find using Google, point me in the right direction if you can), but never was it a standard term used by any major tech company.
Here's just one quick example:
http://the-gadgeteer.com/1998/04/19/palm_iii_review/
This mode lets you show more apps on one screen using little icons. Only the built in apps have the correct mini icons. All your other apps use a generic little diamond like icon. You can also create categories for the applications. A pulldown menu lets you switch between categories. The memory app is now hidden in the launcher menu under Info.