Cognomen Дувняк (Duvnjak 
, Дувняк 
) , in all the world, is quite a common last name. The family name Дувняк is habitual in Southern Europe, particularly Croatia, where it is quite a common surname, Bosnia and Herzegovina, and Serbia (explore the name in all countries).
| VARIANT | COUNTRY |
|---|---|
| Duvnjak | Germany, Serbia, Croatia, Bosnia and Herzegovina, Slovenia |
| Дувняк | Ukraine, Russia |