Last name קוסאק (Kossak 
, Kosak 
, קוסאק 
) , all around the world, is quite a common cognomen. The surname קוסאק is characteristic of Slovenia, where it is quite a common surname, Slovakia, where it is quite a rare surname, and Poland. Measured by absolute frequency, it most frequently occurs in Germany, Poland, and the United States. Also, קוסאק is the forename as well as the last name.