In Croatia, Cernaz families are Italians (from Rovinj ).
Prevalence
Only a few people with faimily name Cernaz live in Croatia today, in one household only. There were 20 of them in the middle of the past century, and their number decreased significantly. They are located in two Croatian cities only, in Rovinj (<5) and Pazin (<5).
Outside Croatia
Family name Cernaz is present in 8 countries on four continents.
In the sources analysed in the project Acta Croatica so far, the name is mentioned over five times, the first time 1917 in source List of Dignitaries, Officials and Public Servants of the Kingdom of Croatia-Slavonia.