A sign in the German language stating "Smoking, open flame and fire prohibited".
German was a Human language spoken on Earth, specifically in the country of Germany.
German was the language spoken by the Nazi regime of the early 20th century. Although many were also proficient in English. (VOY: "The Killing Game, Part I", ENT: "Zero Hour", "Storm Front")
- It's probably unlikely that as many Nazis in real life spoke perfect English, as they did in episodes of Star Trek.
Ensign Hoshi Sato began speaking German while dreaming about her students back on Earth, and again later while attempting to break the lock out code in the decon chamber in 2154, while under the effects of a silicon-based virus. (ENT: "Observer Effect")
An ancient star chart in the German language can be found in the opening credits of Star Trek: Enterprise.
An ancient star chart in German
Wunderkind was a German word meaning "wonderchild". Doctor Paul Stubbs referred to himself and to Wesley Crusher as a wonderchild. Wesley recognized the word as being German. (TNG: "Evolution")
When a holographic Albert Einstein was conversing with Reginald Barclay after his intellect had been enhanced by the Cytherian probe, Einstein exclaimed Grüß Gott when Barclay showed him a revolutionary new way to look at the Theory of General Relativity. (TNG: "The Nth Degree")
- "Grüß Gott" means "Good morning", or "Good day" in English. It is more likely that Einstein meant to say "Mein Gott" which is "My God" in English or "Großer Gott" which is "Great God", which is an exclamation which Einstein would have, in context, been more likely to have used.