Košak families are Croats and they are mostly from Cakovec area. In the past century, relatively most of Croatian residents bearing this family name were born in Cakovec and Zagreb.
Prevalence
About 270 people with faimily name Košak live in Croatia today, in 120 households. There were 260 of them in the middle of the past century, and their number remains constant. They are located in the most of Croatian counties, in 21 cities and 40 other places, mostly in Zagreb (20), Cakovec (20), Rijeka (15), Donji Kraljevec in Prelog area (15), and in Belica in Cakovec area (15).
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.