I recently heard from John Minkowski, whose father Jan Minkowksi was a student of Pauli’s in the late 1940s. He asked if I knew what the specific context of Pauli’s “Not Even Wrong” comment was, and I told him I didn’t. I referred to this early blog post, which explains that Karl von Meyenn (editor of Pauli’s correspondence) had pointed me to a biographical memoir about Pauli by Rudolf Peierls which includes:

Quite recently, a friend showed him the paper of a young physicist which he suspected was not of great value but on which he wanted Pauli’s views. Pauli remarked sadly ‘It is not even wrong.’

Looking around for any more information about this, Wikipedia links to a 1992 letter to the editor at Physics Today from Peierls, which states

Wolfgang Pauli’s remark “Das is nicht einmal falsch” (“That is not even wrong”) was made not as a comment on a seminar talk but as a reaction to a paper by a young theoretician, on which a colleague (I believe it was Sam Goudsmit) had invited Pauli’s opinion.

Google also turned up a translation of a talk by Peierls in this article by Mikhail Shifman, which includes:

Somebody showed to Pauli a work of a young theorist being well aware that the work was not too good but still willing to hear Pauli’s opinion. Pauli read the paper and said, with sadness: “It is not even wrong.”

Trying to guess what the article in question might have been, I’m tempted by the hypothesis that the discussion with Goudsmit was about Everett’s “Relative State” Formulation of Quantum Mechanics paper. The timing (“Quite recently”) would have been right, with the paper published in July 1957, Pauli’s death later in December 1958. Goudsmit at the time was editor-in-chief at Physical Review, so would have been interested in Pauli’s opinion of the paper.

Complicating this story, John Minkowki sent me some pages from his father’s 1991 book Through three wars: The memoirs of Jan Michael Minkowski, which included this (in a context describing his 1946-48 student days at ETH):

I remember a seminar in theoretical physics given by a visitor from another Swiss university. These seminars were presided over by Dr. Pauli, and after the speaker finished all eyes would turn to Pauli to pronounce the verdict in his commentary. This particular lecture was treated by Pauli with progressively faster twirling of his thumbs around and around one another and a growing benevolent smile. Bad sign, we thought. The more he smiled the more vicious he will be, we thought. And sure enough, he smiled some more and said “It isn’t even wrong.”

One possibility here is that Minkowski was mis-remembering something from forty years earlier, another is that the occasion that Peierls was referring to was not the first time Pauli had used the phrase. As evidence for the second hypothesis, see this interview with Konrad Bleuler, which points to the possibility of Stueckelberg as the “visitor from another Swiss university”:

So these seminars took place in a common seminar having also Professor Ernst Stueckelberg, then a Professor in Geneva, also Stueckelberg being a well-known theoretician, his work was very much, if I might remind you of that fact, acknowledged by Richard Feynman. For example, his idea of the particle going back in time being interpreted as an antiparticle came as far as I know originally from Stueckelberg and many other great ideas. I remember one special seminar in which, of course this seminar could be rather called. High Court, with scientific papers in the docket, sometimes really sentenced to death. From that one might record Pauli’s classification of scientific papers. There were two classes or else there were old and right. Or the other class, new and wrong. But hardly anything intermediate. If it was even worse, Pauli would have said “it’s not even wrong.” That was the kind of atmosphere. But all what is written in physics is either understood or else it’s thrown away, and not this half-and-half, what we see at present. But then in this connection it was a search for truth. And for Pauli, a lecture hall was a kind of a holy place where only truth was allowed. And a wrong statement was a sacrilege, and in that sense one should understand his rather extremely sharp remarks he might make to some lecturer who seemed not to present things in a quite logical way. But coming to that special, to another special seminar is the following: Stueckelberg always knew really special — I might say prophetic — ideas. He gave a lecture and of course Pauli — it happened very often — didn’t agree. And said “you are not allowed to say such things.” But you see, Stueckelberg being a prophet, he’s not so easily stopped uttering his prophecies. So Pauli in despair menaced Stueckelberg with a stick and it seemed — I was not present myself but I was told — that the seminar ended like the war of Troy, Pauli, rather corpulent, with his stick after Stueckelberg around the table in the lecture hall. That was the kind of attitude at this period.

I’m not sure what to make of all of this. Perhaps Pauli used the phrase both in the late 40s to criticize Stueckelberg (probably unfairly since many of Stueckelberg’s ideas were ahead of his time) and then Everett in the late 50s (in my opinion accurately, but I don’t want to start up the usual empty arguments about MWI here).