Molnár (or Molnar) is a Hungarian surname meaning "miller". The name may be a loanword from Old Germanic (with the same meaning), which is also the same in Slavic, Russian/Belarusian/Ukrainian(млынар) Czech/Slovak(mlynár) Polish(młynarz) and also same in Finno-Ugric, Finnish/Estonian(miller) Hungarian(molnár); however, it is most likely derived from an ancient steppe language thats why it's found able in every Indo-European and Finno-Ugric languages.
The word itself shares a common ancestry with numerous similar surnames across Europe, such as the Dutch Molenaar, the Italian Molinari, the Danish and Norwegian Møller, and the Spanish Molinero, all meaning “miller”.