After Caesar (which simply happened to be his family name) Octavius took the title Augustus which means better, more, augmented. And most Roman emperors and strong men took the title August thereafter. Their second in command was given the title Caesar/Kaiser. Please correct me if this description is flawed!

But then why didn't emperors later on use the title Augustus rather than Caesar? Besides the King of the Germans calling himself "number two", then most notably, when Napoleon proclaimed himself to be Caesar, wouldn't it have been a great propaganda opportunity for the Austrian king to proclaim himself as Augustus, literally the better of Caesar/Napoleon?