Latin: "German rage".
A phrase first used in the Pharsalia (1:255), by the Roman poet Marcus Annaeus Lucanus. Later, Petrarch wrote (in Rime 5:53) of Tedesco furor (Italian, same meaning). This, again, inspired the French poet Antonius de Arena to coin the phrase Furia franchese (Italian: "French rage").
It is, however, M. Annaeus Lucanus' version which is most used, and often popular among German demagogues and nationalists. In one of his speeches to the German Reichstag, Bismarck said that "furor teutonicus is irresistible". Adolf Hitler, who had a predilection for quoting Bismarck, often repeated this expression.