Whenever this debates comes up everyone always says, "wait, the term existed before OSI", but no, it really did not. Essentially nobody was saying "open source" before 1998 when OSI and Tim O'Reilly started pushing "open source".
https://thebaffler.com/salvos/the-meme-hustler
"Open source" wasn't our idea, and the greatest marketing trick that OSI ever did was convince so many of us that it was.