I didn't know that either, interesting. I don't know about Sicilians but for my own Italian American family, it is customary to name your son after his grandfather and daughter after her grandmother (even after uncles and aunts too). I have a few cousins with the same name because of this. And one entire family has so many Joe's and Jo's for Josephine, you call out Joe/Jo and everybody responds lol. Godfather fans can correct me if I'm wrong but he named him Antonio to follow tradition. Back when Antonio (Anthony) was growing up, it was very customary to take the Americanized version of your name to fit in. You also have a confirmation name in addition to your first and middle name. You take the name of a saint.
You are right ofcourse that this is a Sicilian tradition, particulary in the Mafia. I think it only applies to the first-born son who is named in honor of his grandfather. Therefore, Sonny should have been named after his grandfather Antonio and Anthony after his grandfather Vito. Middle names don't count.
I think both Puzo and Coppola as second generation Italian-Americans who originated from Naples weren't aware of this.
