Borsod was an administrative county (comitatus) of the Kingdom of Hungary. The capital of the county was Miskolc. After World War II, the county was merged with the Hungarian parts of Abaúj-Torna County and Zemplén counties to form Borsod-Abaúj-Zemplén county. The name comes from the personal name Bors (an early medieval magnate) with the -d suffix used to derive place names in old Hungarian language. The personal name Bors could have derived from bors (Hungarian "pepper") and/or derived from Turkish (a theory of János Melich) or from the Slavic personal name Boriš (a theory of Elemér Moór). The problem has not been sufficiently resolved yet. E.g. Lajos Kiss suggests the Turkish origin, whilst Slovak scholars have been suggesting the Slavic origin since the times of Ján Stanislav who accepted Moór's theory as more reliable and pointed to several place names with similar etymology (*Bor[I]ša). Ján Steinhübel points to the Czech name Borša (a member of the retinue of Břetislav II); from the same name derives also e.g. Boršov nad Vltavou. Before World War I, Borsod county shared borders with the counties of Gömör-Kishont, Abaúj-Torna, Zemplén, Szabolcs, Hajdú and Heves. The river Tisza formed the southeastern border, and the river Sajó flowed through the county. Its area was 3,629 km2 around 1910. Borsod is one of the oldest counties of the Kingdom of Hungary. In the early history of the Kingdom of Hungary, each county (in Latin comitatus) formed around a castle (the majority of these castles were motte castles; most of the stone-built castles were constructed after the Mongol invasion of Hungary in the mid-13th century). The castle – which stood near modern-day Edelény – bore the name of its first steward, Bors, who lived during the reigns of either High Prince Géza or his son Stephen I. The county's borders became permanent in the early 14th century, when the neighbouring Torna County was formed, and they remained basically unchanged for the next six hundred years.