iPad getting annoyed by upgrade requests I have an original iPad. I cannot upgrade it anymore because the newer OS's do not work with an original iPad.

Unfortunately, I get incessant upgrade notifications.

Is there any way to turn these off?
As mentioned in the comments, your iPad (MC764LL/A) is an iPad 2, and not the original iPad as mentioned. 
The latest version of iOS on your iPad is iOS 9.3.2. Since you are using iOS 9.1, you will get an update notification. You could, however, choose to ignore it. 
I would suggest you install the new OS. 
To answer your question: No, you cannot turn off the notification for an iOS software update.