A previous post mentioned the term genericide, which is defined as the process by which a brand name becomes a generic name for the product category. I would like to propose an expanded definition of genericide; I think it should also include the process by which a known "person" name becomes a generic, descriptive noun for anyone that has certain characteristics that are associated with that name.
Consider the following names that have already gone through genericide:
Melvin: an uncool person.
Bob: an imaginary friend.
Lolita: a sexually precocious young girl.
Poindexter: a brainy, nerdy boy.
Eugene: see Poindexter.
Velma: the female version of Poindexter.
And of course...
John Doe: an unidentified man.
Jane Doe: an unidentified woman.
I was always more of a Velma than a Lolita in high school.