Bertok families are often Croats and they are mostly from Osijek , less frequently Italians (from Umag ). In the past century, relatively most of Croatian residents bearing this family name were born in Osijek and Umag.
Prevalence
About 90 people with faimily name Bertok live in Croatia today, in 30 households. There were 110 of them in the middle of the past century, and their number decreased by 20 percent. They are located in 7 Croatian counties, in 11 cities and 8 other places, mostly in Umag (15), Ivanovac in Osijek area (10), Djakovo (<10), Vladislavci in Djakovo area (<10), and in Slavonski Brod (<10).
In the sources analysed in the project Acta Croatica so far, the name is mentioned few times, the first time 2007 in source Encyclopaedia of Croatian Surnames.