The 'CC' in emails stands for 'carbon copy' and comes from a 19th-century method of copying documents with carbon paper.

Pellegrino Turri invented carbon paper in 1806. He created it to help a blind friend write letters without getting ink everywhere. The paper was coated with a mixture of wax and carbon black pigment. Writing or typing on the top sheet applied mechanical pressure to the wax layer.This pressure transferred the dark pigment onto the paper underneath. This allowed people to make one or more copies at the same time they wrote the original. Reporters and office clerks used this method for over 150 years to keep records. It was the standard way to duplicate information before photocopiers existed.In the 1970s, computer scientists built the first email systems on a network called ARPANET. They needed a way to show that a message was being sent to more than one person. They chose the term 'CC' because everyone already understood what a carbon copy was. This was officially written into email rules in 1977.Digital 'CC' works differently than physical paper. It uses a system called Simple Mail Transfer Protocol (SMTP) to send the data. The computer makes perfect digital copies of the text and sends them to different addresses at once. Unlike paper, digital copies do not get lighter or fuzzier no matter how many you make.