cc used to stand for carbon copy, back when they had them. It was what you typed, on a typewriter, to show for whom you were making copies, and then the people getting the carbon copies didn't wonder why they were reading something addressed to someone else. So it still does in the mind of everyone old enough to have known it when it meant that. It's probably pronounced see-see now, so younger people don't realize the connection.

Also, my kid said someone "called it in all year" and I thought, I bet they email it in nowadays, those journalists who don't actually GO to the races or the opera or the riot or the council meetings or whatever.

I hadn't heard that phrase since I was a little'n, dad was a newspaper reporter back in the day. Before I was born but he liked some of the phraseology.