Others believe the word originates from Sarmatian bajan. According to one theory, the title of ban derived from the name of an Avar khagan, Bajan. There are alternative theories concerning Illyrian origin and the Illyrian name Banius, which is to be found on Illyrian remains in Bosnia.
The title was further on used in Wallachia from the 14th century up to 1831 (where it was associated with the highest boyar office and the region of Oltenia), medieval Moldavia, the Kingdom of Serbia and Kingdom of Yugoslavia between 1929 and 1941. The meaning of the title changed with time — the position of a ban can be compared to that of a viceroy or a high vassal such as a hereditary duke, but neither is accurate for all historical bans. The territory ruled by a ban was called banat or banovina, often transcribed to English as banate, banat, bannat, etc.
Bans were also provincial administrators in the Kingdom of Hungary, where each of the provinces was called banat; the Croatian word for province was banovina. Bans usually administered regions outside the kingdom, but within the realm.
After Croats elected Hungarian kings as kings of Croatia in 1102, the title of ban acquired the meaning of viceroy because the bans were appointed by the king, though Croatia, remaining a Kingdom in personal union with Hungary, was not referred to as a banovina (banate). Croatia was governed by the 'viceroyal' ban as a whole between 1102 and 1225, when it was split into two separate banovinas: Slavonia and Croatia. Two different bans were occasionally appointed until 1476, when the institution of a single ban was resumed, and lasted until 1918. One of the most distinguished bans in Croatian history was Toma II. Erdödy, great warrior and statesman in one person, Croatia owes him much for protecting her rights against the Hungarian nobility, his mostly known words in Latin are Regnum regno non praescribit leges, 'a kingdom may not impose laws to a(nother) kingdom'.
When the medieval Bosnian state achieved a certain level of independence in the 12th century, its rulers were once again called bans, and their territory banovina, likely because of the similar suzerain status that it had towards the king of Hungary. Nevertheless, the Bosnian bans weren't viceroys in the sense they were appointed by the king. Sometimes their title is translated as duke. Later in the 13th century they gradually achieved more independence (though in some periods they were still vassals) and eventually proclaimed themselves kings in the late 14th century.
The region of Mačva (now in Serbia) was also ruled by bans. Mačva was part of the medieval Hungarian kingdom though under various levels of independence; some of the bans were foreign viceroys, some were native nobles, and one even rose to the status of a royal palatine.
Ban was also the title of medieval rulers of parts of Wallachia (Oltenia and Severin) since the 13th century. The Wallachian bans were military governors; their jurisdictions in Wallachia were called banats. The main Wallachian ruler was titled voivod, the position bans aspired to.
The region of Banat (sometimes called the Temeswarer Banat) in the Pannonian plain between the Danube and the Tisza rivers, now in Romania, Serbia and Hungary, however got its name without ever being ruled by a ban.
A region in central Croatia, south of Sisak, is called Banovina or Banija. The origin of the names of Banova Jaruga, city in Croatia, and Banja Luka and Banovići, cities in Bosnia and Herzegovina, could be also from the word ban.
The term ban is still used in the phrase banski dvori ("ban's court") for the buildings that host the highest government officials. The Banski Dvori in Zagreb host the Government of Croatia, while the Banski Dvori in Banja Luka host the President of Republika Srpska (first-tier subdivision of Bosnia and Herzegovina). The building known as "Bela banovina" ("the white banovina") in Novi Sad host the parliament and government of the Autonomous Province of Vojvodina in Serbia (The building got this name because it previously hosted administration of Danube Banovina).