Brumnjak families are Croats and they are mostly from Opatija. In the past century, relatively most of Croatian residents bearing this family name were born in Rijeka and Opatija. In Mala Učka in Opatija nearly every inhabitant had the family name Brumnjak.
Prevalence
About 70 people with faimily name Brumnjak live in Croatia today, in 30 households. There were 90 of them in the middle of the past century, and their number decreased by 20 percent. They are located in threee Croatian counties, in 6 cities and 12 other places, mostly in Icici (20), Poljane (<10), Vela Ucka (<10), Rijeka (<10), and in Opatija (<5).
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.