The history in Germany goes back to post WWII. As you may know there was a shortage of workforce after the war. Most able bodied individuals were used in the war as foot soldiers. So when building the country back up became a priority they needed workers. They looked to Turkey for that labor force. The Turkish came here and didn't want to leave and, they found they had food people liked to eat. Some dude in Berlin altered the taste to fit the German pallet (made it less spicy) and that's how Donner is sold today.
Today after coach had me run 100 minutes, I decided I was hungry for Donner and so I went to our favorite truck. Yes, the picture below is where I bought it. Can you believe Super Dave is buying his food from a truck. Did I ever step foot outside the RRS buiding as the coach pulled up to sell breakfast? No of course not, but here in Germany why not. This truck actually never leaves its spot. It's always there. The guy behind the counter is super freindly and is always happy to serve.