Firstly, Is it true that Puzo really didn’t have that much knowledge about the mafia? Wouldn’t Vito and Michael be called “Don Vito” and “Don Michael” instead of “Don Corleone”? Or am I incorrect? Also, did people in the mob use the term “Godfather” to refer to their boss prior to the movie coming out?

Puzo said after GF was released that, growing up in the Hell's Kitchen neighborhood of NYC, he was aware only of the lowest-level street activity of the Mafia. As a gambler who owed money to loan sharks (the reason he wrote the novel), he was also aware of how illegal gambling worked. That's what he admitted to.

Hard to know how Dons are referred to--never spoke to one.

I can’t say I’ve spoken to one either lol. Did he do a lot of research about the inner workings? Because he really talked more about the upper level of the mafia than the lower level. But many monsters believe that The Godfather for the most part was very accurate. That also could be a credit to Coppola perhaps being familiar with the inner workings of the mafia

I believe someone here said before that Puzo covered the Bonanno family for a New York newspaper. This would make sense because the Bonannos, especially under Joe himself, and the Profacis were the two perennially Sicilian-centric families like the Corleones were.

If that’s the case, then maybe that’s where he got his knowledge from. I believe the term “Godfather” was used in the mafia before the movie came along but I cannot say for sure. Puzo said it was not if I recall correctly. He may have forgotten where he may have heard it.