Ćosić families are mainly Croats and they are mostly from Bosnian Krajina , barely Serbs and Bosniaks (from Bosnian Posavina ). In the past century, relatively most of Croatian residents bearing this family name were born in Bosnian Krajina (Teslic area) and in Banja Luka Region, Bosnia (Banja Luka area). In Priječani in Banja Luka Region (Bosnia) every third inhabitant had the family name Ćosić.
Prevalence
About 4200 people with faimily name Ćosić live in Croatia today, in 1700 households. There were 1000 of them in the middle of the past century, and their number multiplied. They are located in all Croatian counties, in 96 cities and 381 other places, mostly in Zagreb (795), Slavonski Brod (230), Split (220), Osijek (140), and in Sesvete (100).
In the sources analysed in the project Acta Croatica so far, the name is mentioned over fifty times, the first time 1902 in source Hartmann's General List of Apartments in Zagreb.