1With following word used as if a surname: (a name given to) a hypothetical ordinary or average person of the specified type or associated with the thing named, as "John Q. Citizen", "John Q. Public", "John Q. Taxpayer", etc.
Originally in John Q. Public: see note at the etymology.
2A hypothetical ordinary or average person; the general public collectively.
1920s; earliest use found in Evening Mail (New York). Originally (in John Q. Public) from the male forename John + Q (presented as a middle initial) + public, apparently as an alteration of earlier John Public, used as a name for a hypothetical ordinary member of the public.