If it helps, dogs are supposed to respond better to names with "t", "x" and "sss" sounds in them. Their ears hear these sounds louder and clearer than humans do so the idea is that if, it sounds louder they can hear it better, and therefore respond faster. It can also help with training if because they can be sure you are saying their name, and learn faster because you can demand their attention easier. Could explain why you always see 'smart' dogs called Rex and Max around! I know my Max is super smart as well!