The first interpretation of the name was suggested by Antonio Bonfini. He tried to explain it from "Istrogranum", "city at the confluence of "Ister" (the Greek name of the Danube river) and "Gran" (the Latin name of the river Hron)". This interpretation is still popular. Viktor Récsey attempted to derive the name from Germanic languages. After the conquest of the country by Charlemagne, the Franks should give the name Osterringun to their easternmost castle; as a comparison, a reference is made to the town of Östringen. Pavel Jozef Šafárik tried to explain the name from Slavic "ostřehu" (). Gyula Pauler suggested a Slavic personal name "Stigran" without a deeper analysis of its origin.