Is there an official original source on how the "insider" wrestling terminology (face, heel, work, kayfabe, etc…) came to the regular masses? Retired wrestler spilling the beans? One of the first wrestling reporters creating them? Just something wrestlers gave up in an interview once to let the viewer get more of an understanding?
A lot of it was the Observer in the 80s. In the really old ones that we covered, somewhere around 1985 Dave switches from "good guys" to "babyfaces" and starts using a lot of the terminology that was kayfabed up until that point. I think Jim Cornette, being one of Dave's biggest sources, had a lot to do with letting it all get out. Mostly it was just the business changing and wrestlers thinking that they could make more money by "pulling back the curtain", only to reveal that there was in fact a more secret curtain behind the first one. That was kind of the Russo philosophy and why there was so many backstage segments in the Attitude Era — they were trying to make the viewer feel like they were going backstage, even though they were only going to the staged backstage.