The prestigious surname Katz is a symbol of the Jewish culture, which has been found in many places all over the world. In the Middle Ages, most people were known only by one name. As people began to settle closer to one another in towns and cities, it became more important to be able to identify people. As such, hereditary surnames arose. The surname Katz is an occupational surname, which comes from the Hebrew phrase "kohen Tsedek," which means "priest of righteousness."
In the United States, the name Katz is the 1,176th most popular surname with an estimated 24,870 people with that name.  However, in France, the name Katz is ranked the 8,856th most popular surname with an estimated 500 - 1,000 people with that name. 
^ Filby, P. William, Meyer, Mary K., Passenger and immigration lists index : a guide to published arrival records of about 500,000 passengers who came to the United States and Canada in the seventeenth, eighteenth, and nineteenth centuries. 1982-1985 Cumulated Supplements in Four Volumes Detroit, Mich. : Gale Research Co., 1985, Print (ISBN 0-8103-1795-8)