Czargrad

Tsargrad is a Slavic name for the city or land of Constantinople, the capital of the Eastern Roman (Byzantine) Empire, and present-day Istanbul in Turkey. It is rendered in several ways depending on the language, for instance Old Church Slavonic: Цѣсарьградъ; Church Slavonic; Царьгра̀дъ, Russian: Царьгра́д; South Slavic languages: Carigrad or Цариград, depending on their alphabets (or Tsarigrad as an alternative Latin transliteration of Cyrillic); Slovak: Carihrad; Czech: Cařihrad; Polish: Carogród; Ukrainian: Царгород; also Czargrad and Tzargrad; see Tsar.

Tsargrad is an Old Church Slavonic translation of the Greek Βασιλὶς Πόλις. Combining the Slavonic words tsar for "Caesar / Emperor" and grad for "city", it stood for "the City of the Caesar". According to Per Thomsen, the Old Russian form influenced an Old Norse appellation of Constantinople, Miklagard (Мikligarðr).

Bulgarians also applied the word to Tarnovgrad (Tsarevgrad Tarnov, "Imperial City of Tarnov"), one of the capitals of the Bulgarian tsars, but after the Balkans fell under Ottoman rule, the Bulgarian word has been used exclusively as another name of Constantinople.

...
Wikipedia