Every time you CC someone, you’re describing a piece of stationery. Before email, to send a copy of a letter you slid a sheet of carbon paper — inky on one side — behind the page. The pressure of each typewriter key printed the character onto the sheet below at the same time. The person who received that duplicate had been carbon-copied.
BCC is the best part: blind carbon copy. In the paper world you’d type an extra copy for someone the main recipient never knew about — their name simply wasn’t on the visible letter. The interface kept the exact etiquette, and the exact quiet power move, of a 200-year-old office supply.
So the header of the most modern message you send today is written in a dead language, and everyone still speaks it fluently without knowing a single word’s origin.
The object died. The metaphor didn’t.