General Discussion

Probably earlier. But that's the oldest movies I've watched that used the term. Hey, some were in theaters even before Trump was born!

Not divided or shared with others.
"exclusive publishing rights."

And there you have it. They were the only ones to have the story to publish, it was theirs to publish, if they didn't nobody else would have. Want the story, you go to them; they had a monopoly. Unlike a story from a press briefing, where there's a gaggle to pick up the story and they used to race to get the story in first. Then the first was merely "first." Or reporting on a hurricane, where the reporter reports for the public that's in the hurricane that--hey, look, surprise, there's a hurricane!

https://www.wordnik.com/words/exclusive tends to be a quick 3-second Google search away for daunting questions about meanings.