I still think it's funny going from the PT to the OT, with the PT's emphasis on the Sith and mentioning the name in every other scene to not hear it uttered once in the OT. Not that I blame Lucas or anybody else for this. Just find it amusing.One important thing about the Sith is that prior to the PT, the word was out there...various offscreen sources referred to Vader as the "Dark Lord of the Sith"...but it wasn't made clear that the Sith were supposed to be the dark counterpart to the Jedi order. Some offscreen sources tried to explain what "Dark Lord of the Sith" meant in entirely different ways...the Noghri in Zahn's novels were originally going to be called the Sith, but the Lucas continuity cops killed that.
It would be like if, in a fictional cold war analogy, two Soviets somehow managed to become elected president and VP and turn America into an Empire.
20 years later, the equivalent of Obi Wan, living underground in Beowawe, Nevada explains to his cousin that the VP was a friend of his who simply turned to evil. No mention of the Soviets.
Outside of the Jedi I don't recall anybody mentioning the Sith in prequels, so I don't think knowledge of them was as common as let on.
+1 on this. This is why it's never really bothered me that no one mentions Sith in the OT. Who really who would know about it in the general populace? We spend most of our time in the PT with Jedi who know about the Sith all too well because it relates specifically to their secret order, while in the OT we spend our time with the regular folk, who never would be exposed to that term in their normal, work-a-day lives.