CWBorne said:

-The term "Sith" is thrown around much less and not even mentioned on screen in the OT.

When I was a wee lad I got a Darth Vader action figure that came with a collector's coin, it had Vader's head on it and said "Dark Lord of the Sith" on it. I thought it was a real word and asked my dad what "sith" meant. I remember very clearly he was sitting in his study with his nose buried in some reference works, his massive office chair slowly spun around as he turned to face me with a puzzled look on his face. After a moment he noticed the coin in my hand and immediately said, "Oh, it's a dark Jedi" and turned back to his books.

I wonder how he knew that? I'm just now realizing how weird that is, he wasn't into Star Wars, so I have a hard time imagining him reading up on it outside of the films.