Cognomen קלאק (Clack 
, קלאק 
) , in the entire world, is quite a common last name. The surname קלאק is characteristic of Reunion, where it is quite a common surname, the United Kingdom, where it is quite a rare surname, and Australia. Measured by absolute frequency, it is commonest in the United States, the United Kingdom, and South Africa. Much less frequently, קלאק is the forename as well as the last name.