Trojak families are Croats and they are mostly from Varazdin. In the past century, relatively most of Croatian residents bearing this family name were born in Varazdin and Zagreb.
Prevalence
About 120 people with faimily name Trojak live in Croatia today, in 50 households. There were 90 of them in the middle of the past century, and their number increased by 30 percent. They are located in 8 Croatian counties, in 9 cities and 11 other places, mostly in Zagreb (35), Varazdin (35), Koprivnica (<10), Nedelisce in Cakovec area (<10), and in Prokljuvani (<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.