I followed the track for this car. Gillie Tyrer modified it extensively and I have found all this names Supermoter, FIAT-BMW, FIAT-Supermotor, BMW Special but I could not find none in German and of course the name you are looking for. It is clear that at least at sometime it had a FIAT 1500 cc engine, although I think it was changed for a BMW engine later. I dont know if this engine is like its original engine or other, but I've seen this car has raced in several events to classic, GP Mutschellen 2012 and 2013 Classic Ransel among others, and in one of them was listed as driven by Stephan Kühnis from Oberhasli and its engine was a 1990 cmm and 150PS. Maybe the word you are looking for refers to its original engine or the other engines.
Thanks for the hint mekubb but given my knowledge of German I think I am not going to be able to give the name you are looking, because every time I run a page in German all words with 8 letters are possible for me. These months I'm very busy with personal matters and I think I will not have time for many more searches in some time, so you can unlock it for giving the chance to others for solving easily, I had so much fun and I want to know his name. I will try to post other photos when possible but for the moment I leave a photo of this car with other nose.