It was a common colloquialism in news reports years ago. It's hard to take note of when something stops getting said. Decades could pass before you notice that something has disappeared from the language. Maybe the death of "the man in the street" began in the 1970s, with the success of the women's movement, as it became less and less possible for mainstream folks to convince themselves that "man" includes woman. Perhaps there was a transitional period in which reporters — perhaps literally in the street with their microphones seeking random comments from passersby — said "the man — or woman — in the street," before that got old and sounded corny and then nobody ever said it again.
Yesterday, Meade and I were watching "Jeopardy!" It's "College Championship" time and all the players are college students. The board full of answers in need of questions is stocked with things that younger people know — pop singers, movie superheroes, school-level math, history, and science and so forth. The kids buzz in and get many questions right. But yesterday, they had an answer that drew absolutely vacant stares and even puzzlement when Alex Trebek revealed the question. The answer was: The middle initial of John Public. The question: What is Q? I laughed a lot, because I could see that from the kids' perspective, that was just some weird nonsense.
Nobody says "John Q. Public" anymore. Like "man in the street," the term embodies the general public in a single person. This time, that person has a name, John Q. Public. I'm going to assume, it's gone away because we won't accept the idea that the public can be personified as a male, and that also means the whole idea of the general public as one person just doesn't work anymore. If there was ever a period when people adapted to changing times by saying, cutesily, "John Q. — and Jane Q. — Public," I missed it.
Now, it just seems goofy, I suppose, to people who don't remember the common usage, to hear that John Public has a middle initial and it's Q. What's the Q for? From the OED:
1937 N. & Q. 6 Mar. 177/2 ‘John Citizen’..is not so frequent in American usage as ‘John Q. Public’... It is probably a play on the name of an early president, John Q(uincy) Adams.I think it's more like Jesus H. Christ. An initial just seems funny. And if you want funny, there's no funnier letter than Q.
As for Jesus H. Christ, well, what's that about? Hilariously, there's a Wikipedia entry for Jesus H. Christ — which, you may realize, is "a vulgarism" that "is not used in the context of Christian worship." Mark Twain referred to it in his autobiography as typical of "the common swearers of the region," so the usage goes way back. Some people attribute it to "the first three letters of the Greek name of Jesus (Ἰησοῦς)... transliterated iota-eta-sigma, which can look like IHS." There's also an idea that the H is for Harold — from mishearing "hallowed be thy name" the Lord's Prayer as Harold be thy name.
IN THE COMMENTS: Paddy O said "Monty Python had man in the street segments":