Both czar or Tsar (Russia) and kaiser (Germany) were derived from the name of Julius Caesar, leader of ancient Rome.
Czar is a title used to designate certain monarchs or rulers, and is a Slavic term with Bulgarian origins which is derived from the word Cæsar, meaning Emperor in the European medieval context.
The first ruler in Bulgaria to adopt the title tsar was Simeon I.
The last person to bear the title Tsar was the last Tsar of Bulgaria, Simeon Saxe-Coburg-Gotha.
More recent use of the term in the U.S. include the title “czar” as a slang term for some high-level civil servants, such as the “drug czar” for the director of the Office of National Drug Control Policy.