tsar: [16] Caesar was a Roman cognomen (English gets caesarian from it) and from the days of Augustus was used as part of the title of ‘emperor’. The Germanic peoples took it over in this sense (it is the source of German kaiser) and passed it on to prehistoric Slavic as *tsēsari. This has evolved into Serbo-Croat and Bulgarian tsar and Russian tsar’ – source of English tsar. => caesar
