Dutch is used by English-speaking people to refer to the language and people from Holland. It stems from the term which Dutch people traditionally used for their language, i.e. "Diets."

The German people people still call their language "Deutsch"

Both languages belong to the same language group i.e. Germanic (english belongs to this group as well).

The Netherlands (meaning the lowlands) is associated with Holland and Belgium; until the 19th century they were one country. Dutch is the language of Holland and one of the languages of Belgium (i.e. Flemish, which is a variety of Dutch).

Calling a Dutch person German is an insult equivalent to calling a Scottish person English.

Groeten