I suppose the term was being used long before it would have appeared verbatim in any newspaper interviews?
Jack Beckley is quoted as using the term when he had to tell Valerie Bettenhausen of her husband's death, May 12 1961 - though the book that quotes the conversation was published in 1982. Incidentally that same car had won the 1959 Indy 500, so it wasn't always a shitbox.
I suspect the phrase was in use long before then anyway.
Yes, in general words first discovered in print after searches tend to turn up in a context that suggests the usage would already be known, which is frustrating because it shows it’s even older. Some of it I guess is the word just isn’t written in print, maybe others are lost but complicated here by the fact it contains a word often deemed not suitable for print. So I guess I’m also interested in people’s memories of being around cars and memories of it being in use, as well as print examples.
As a prosaic example of this sort of thing, I was very interested in a tv show trying to find the origin of the Liverpool expression ‘made up’ ( to mean something like ‘very pleased’). At the time of making the show, the earliest recorded example was in a tv interview with Ringo Starr where, again, it is clear he is expressing himself in such a way that it was already in common usage. As it was part of my late grandmother’s lexicon, almost certainly the expression is waaaaay older but the proof is difficult.