Here's why:
* No standardized German: A standard, unified German language did not exist before the 19th century. Each region had its own dialect, often significantly different from others.
* High German vs. Low German: There were two major groups of dialects: High German, spoken in the south and central parts, and Low German, spoken in the north.
* Literary language: While dialects were common in everyday life, a more formal, literary language based on High German dialects was used in writing and formal communication. This language was called Hochdeutsch (High German).
It wasn't until the 19th century that efforts to unify the language through standardization, education, and the use of Standard German began to take hold. This process was aided by factors like the rise of nationalism and the need for a common language in a unified Germany.
So, while "German" was the overarching term, the specific language spoken in 1800 depended on the region and the context of communication.