Explanations/etymology also appreciated!
For Joe Shmoe, it means a very average or below average person. It’s a derivation of the practice of using “shm-” to dismiss something (eg “Practice shmactice. We’re already perfect”).
And “John Smith” is meant to be the most average name or person imaginable, so they have the “most common” (citation needed) first and last name as well.
There’s also a name that expresses the same feeling of ‘Joe Schmoe’ in pt-br: ‘Zé Roela’
And to expand on Fulano’s family, we must not forget Beltrano and Ciclano.