I don't know what CC is.
CC MEANS:
Carbon Copy. Olden days, carbon paper was physically placed between the papers - to make a CC, up to 3 or 4 copies - they got worse, the more one made.
Carbon copy of the original - that's when white-out came to be. A white-out changed the original. Carbon copies didn't change. Copiers did not exist then.
Gads.
Maybe some folks are too young...or just don't know, however--
It's all built off keyboards/typewriting.
Some folks just don't know.
PC means private copy
ETC!