The Samogitian dialect should not be confused with the interdialect of the Lithuanian language as spoken in the Duchy of Samogitia before Lithuanian became a written language, which later developed into one of the two variants of written Lithuanian used in the Grand Duchy of Lithuania based on the so-called middle dialect of the Kėdainiai region. This was called the Samogitian (Žemaitian) language; the term "Lithuanian language" then referred to the other variant, which had been based on the eastern Aukštaitian dialects centred around the capital Vilnius; Samogitian was generally used in the Samogitian Diocese while Lithuanian was generally used in the Vilna Diocese. This Samogitian language was based on western Aukštaitian dialects and is unrelated to what is today called the Samogitian dialect; it is instead the direct ancestor of the modern Lithuanian literary language.