Was Herman born in Saxony before Prussia took it over? There were a lot of boundary changes when the Holy Roman Empire collapsed in 1848. Eventually, the northern part was replaced by the Netherlands and Germany (which was previously called Prussia). The southern part of the HRE had previously been split off into Switzerland, Austria, the Vatican City, etc.
I don't know if it existed in 1815, but Germany didn't. The people spoke German. The individual provinces in the HRE confederacy survived on their own before they were taken over by Prussia. Prussia, Austria-Hungary, and Russia had previously carved up Poland. Each was vying for more control of Central Europe and eventually Prussia took it over.
It wasn't till after World War I when Germany, Austria-Hungary, and the Ottoman Empire (now Turkey) got carved up
I've not been able to find a reference to the "town" of Ginsteach, but the spelling of its name isn't very Germanic.