Although he was known as the "Duke of Athens" from the foundation of the duchy in 1205, the title did not become official until 1260. Instead, Otto proclaimed himself "Lord of Athens" (in Latin Dominus Athenarum, in French Sire d'Athenes). The local Greeks called the dukes "Megas Kyris" (Greek: Μέγας Κύρης, "Great Lord"), from which the shortened form "Megaskyr", often used even by the Franks to refer to the Duke of Athens, is derived.