The term "attache case" is defined as a shallow and rectangular briefcase with a handle. The term has roots from the Latin word "attache" meaning to attach or a person/group associated with an embassy or foreign service. The word because associated with briefcases as many of the early diplomats used these cases to transport sensitive documents.
Attache cases are usually manufactured in the form of a rectangle and run anywhere from 4-8 inches thick. Many feature a hard sided material like aluminum for protection, although soft sided attache cases are becoming more popular.