In Croatia, Trnak families are Croats (from Bjelovar area ). In the past century, relatively most of Croatian residents bearing this family name were born in Ilok.
Prevalence
About 10 people with faimily name Trnak live in Croatia today, in four households only. There were 10 of them in the middle of the past century, and their number remains constant. They are located in only threee Croatian places: in Bapska (15), Sasovac in Bjelovar area (<10), and in Osijek (<5).