Cognomen Ivančak (Иванчак 
, Ivančak 
) , in all the world, is a very rare family name. The cognomen Ivančak is characteristic of Belarus, where it is a rare surname, Kazakhstan, and Croatia, where it is a very rare surname. Not in comparison with a country's population, this name is the most popular in Russia, Kazakhstan, and Belarus. Much less frequently, Ivančak is the forename as well as the last name.