> This isn't common at all. What country are you thinking of?
Very very common in my childhood in the northeastern and mid Atlantic United States. I have heard it from west coaters too.
No answer to the nickname "Smitty"? It is a common one, derived from Smith. You can Google it.
> There are modern people today with a surname of Caesar. Somehow, the name of the late celebrity Sid Caesar pops up for me. Wikipedia has more
Not really relevant when the claim was that (1) Little Caesars is named after someone's surname; and/or (2) Caesar was Julius Caesar's surname. Both of those claims are obviously false.
> yes clearly, McDonald's and Hardee's are named for surnames.
But I've been saying this whole time that "Taco Smith" is not similar to "Taco John's", because "Taco John's" is named after a notional owner, Taco John, whereas you couldn't call someone "Taco Smith". (And of course, even if you did, you wouldn't expect the restaurant to have the same name as the owner.)
McDonald's and Hardee's are not evidence that anyone ever referred to anyone as "McDonald" or "Hardee". They're names, not nicknames.
> But yes, it is common to address people by their last name as a nickname. I seem to recall it was especially common back in school, something guys did kind of informally. Plenty of reasons explained here: https://www.google.com/
This isn't common at all. What country are you thinking of?