Well, it was essentially dumb luck to have found those sightings, but I appreciate the appreciation!
Some random thoughts, not that I know more than anyone else, in case anyone’s interested in further discussion.
Something that strikes me as significant about four of the five earliest sightings (1956-1962) is that they’re used nonchalantly and casually, without the authors (and editors) feeling the need to explain the expression to readers. There are no quotation marks around the “the whole nine yards,” “the entire nine yards,” and “all nine yards” in any of the four earliest examples. (I suppose there may have been an assumption that readers could figure out meaning from context.) Wegner’s 1962 short story, in which he has the narrator clarify that “the whole nine yards” was something a brush salesman was fond of saying, uses “the whole nine yards” a little self-consciously. The same vague attempt at clarification is found in the 1964 piece on NASA slang (of course), Charles Coombs’s Aerospace Pilot (1964), and in some class notes from West Point’s Class of 1941 (1965).
I’m not sure how significant that is, but to me it suggests that the expression had been around for a while, at least in some pocket(s) of the country, at least by the mid-1950s and that—as it spread—authors who (I’m guessing) had no long-term experience with the expression figured that readers might appreciate some elaboration. Perhaps that’s an obvious point, but it seems meaningful to me somehow.
Additionally, something (admittedly, an n=1) that for me argues against a specific WWII connection (in addition to Dave’s excellent point about WWII slang being well documented) is that Col. Burton C. Andrus, Jr., a member of that West Point Class of 1941, used “‘the whole 9 yards’ as the teenagers say” in 1965 (note quotation marks and clarification about who was using the phrase).
According to his 2004 obituary, “Col. Andrus was a World War II Army Air Corp. Veteran serving honorably as squadron Commander of B-24s in southern Italy. After WWII he became a Wing commander of B-47s at Dyess AFB and later Wing Commander of the first operational Minute Man Missiles at Malmstrom AFB.” Unless in 1965 he was using “‘the whole 9 yards’ as the teenagers say” ironically, I think this indicates that Andrus found “the whole nine yards” to be pretty novel, though perhaps I’m reading too much into how he qualified “the whole nine yards.”
It’s hard not to go a little crazy mulling over different possibilities. I try not to think too hard about all this, reminding myself that we’re now generally at the mercy of digitizers of books, magazines, newspapers, and the like for what early sightings we stumble upon. It’s not like we’re getting an even sampling across professions, interests, and regions. What I convince myself of at any moment about “the whole nine yards” is probably pretty skewed by where we’re finding these examples; no doubt it existed elsewhere and still lies dormant. Still, as Jim points out, this is a lot of fun.