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.
In US legal cases, “John Doe”, “Jane Roe”, and similar names are used for pseudonymized legal parties.
For instance, the plaintiff in the famous abortion case Roe v. Wade was one Norma McCorvey, identified as “Jane Roe”.
A group of unidentified people appearing as plaintiffs or defendants may be called a group of “Does”, from the name John Doe.
The words doe and roe both refer to deer, which are common wild animals in North America — and as wild animals, represent an arbitrary unspecified person. A doe is a female deer; and while “roe” can also mean fish eggs, roe deer is a common European species of deer.