Carbon copy
Carbon Copy is produced when a sheet of carbon paper is placed between two sheets of writing paper.  As a pen, pencil, or typerwriter element presses down to write on the first sheet, exactly the same writing appears on the second sheet.  The same is true if the two sheets of paper and carbon paper are placed into a typerwriter to generate two copies of a document. People would type "cc" at the bottom of the paper to show where the carbon copy was sent. When people began using email, the carbon copy (cc) shows that the same email is sent to more than one person.