Last name Trnik (Trnik 
) , all around the world, is a rare family name. The surname Trnik is habitual in Slovakia, where it is quite a rare surname, Slovenia, and Austria, where it is a rare surname. Measured by absolute frequency, it most frequently occurs in Slovakia, Slovenia, and Czechia.
| VARIANT | COUNTRY |
|---|---|
| Trnik | Canada, Czechia, Austria, Slovakia, Slovenia |