Last name Dempniak (Dempniak 
) , throughout the world, is a very rare cognomen. The cognomen Dempniak is habitual in Poland, where it is a rare surname, Georgia, where it is a very rare surname, and Canada, where it is an extremely rare surname. Not in comparison with a country's population, it is commonest in Poland, Germany, and the United States. Likewise, Dempniak is the forename as well as the last name.