Probably you missed it, but Wiki explains it more or less. While Britian invented the term "Tank" and the Germans did lend this term at the beginning, they stopped sticking to it very early. Since this new weapon was just an "armoured vehicle", a "gepanzerter wagen", it was a rational move to go with the german word "Panzer" for it. Even the first german version was already called "StPzKrW A7V"=SturmPanzerKraftWagen. That was 1917, so if you meant by nationalism the actual nationalsocialists, it had rather nothing to do with them.