Newer form of the Old Church Slavic name Іѡаннъ (Ioannŭ), which was derived from Greek Ioannes (see John). This was the name of six Russian rulers, including the 15th-century Ivan III the Great and 16th-century Ivan IV the Terrible, the first tsar of Russia. It was also borne by nine emperors of Bulgaria. Other notable bearers include the Russian author Ivan Turgenev (1818-1883), who wrote Fathers and Sons, and the Russian physiologist Ivan Pavlov (1849-1936), who is best known for his discovery...