According to Oda they are part of the greater Ryu family, which in terms of etymology is equivalent to the "saur" in their English names and could be adapted to "saurian". So it's likely that we all thought that Oda named that family as such because of a direct reference to dragons, making Kaido the user of its mythical model, but reality is that he was just using the common denominator to the Japanese terms for dinosaurs, pterosaurs, lizards, etc.; which happens to be "ryu".