I'm not sure what you mean by the creation of modern Germany.

The first unified German state was the German Empire formed in 1871, and before then I don't believe the German language was vastly different from its modern incarnation.

Can you clarify the question, please?

EDIT: Misread. I thought you asked what it was LIKE before the creation of modern Germany. As for what it was called...German. The IDEA of a national German identity and ethnicity existed before there was an actual German state.

You'd probably have to go back quite a while to find it called something other than German, and by then I'm not sure it would be recognizably German, anyway.

In English, the words "German" and "Germany" (or similar iterations thereof, such as "Germayn") have been in use since the 14th century, well before the creation of the modern unified German state in 1871. The words are directly related to "Germania," the Roman and Greek term for the region. In Middle English, the terms "Almain" (for the language) and "Almaine" (for the country) were also used.

Swedish sources about Swedish warfare in Germany, primarily during the 30 years' war usually make distinctions between Plattyska (Low German) and Högtyska (High German). The former was spoken along the Baltic coast and in Brandenburg and the North Sea coast. The latter was spoken in Bavaria, Austria, Sudet and Bohemia and so on.

However, both were considered German languages.

The page on etymonline for German would probably be of interest to you.