Kaiser is the German title meaning "Emperor". Like the Russian Czar it is directly derived from the Roman Emperors' title of Caesar, which in turn is derived from the personal name of a branch of the gens (clan) Julia, to which Gaius Julius Caesar, the forebear of the first imperial family, belonged. Although the British monarchs styled "Emperor of India" were also called "Kaisar-i-Hind" in Hindi and Urdu, this word, although ultimately sharing the same Latin origin, is derived from the Greek Kaisar, not the German Kaiser.
In English, the term the Kaiser is usually reserved for the Emperors of the German Empire, the emperors of the Austrian Empire and those of the Austro-Hungarian Empire. During the First World War, the term the Kaiser — especially as applied to Wilhelm II of Germany — gained considerable pejorative connotations in English-speaking countries.