"Single" + superlative

[Douglas G. Wilson]

When and why did the construction "the [superlative] single [noun]" become
largely supplanted by "the single [superlative] [noun]"?

For example, "the largest single contributor" is outnumbered on the Web
(Google) by "the single largest contributor", although the latter
presumably is almost always (IMHO) either an inept/incorrect expression of
the former or a meaninglessly/incorrectly augmented expression like "the
very largest contributor".

By comparison, "most important single" gets 41 hits at MoA (composite),
"single most important" zero, while MoA has 50 hits for "greatest single",
zero for "single greatest" (actually 1, but that one's erroneous on
inspection). So it was different in the 19th Century, I guess.

In "the single largest contributor", I suppose "single" might be seen as an
intensifying adverb, like "very"; my handy dictionaries don't show any such
adverb.

Alternative interpretations would be (1) "the single largest" = "the single
and the largest", which is either tautological or inconsistent, (2) "the
single largest" = "the only largest", implying merely that there was not a
tie for "largest", theoretically reasonable perhaps, but I think hardly
ever necessary and hardly ever the intended sense.

I think often "single largest" means "largest single": then why not use
"largest single"?

Here is an example from "American Speech" (76:163): Lighter is quoted as
saying (approximately) that the military is the largest contributor to
slang (although he is also quoted as saying that most slang is not of
military origin):

<<the nation's armed forces ... appear to have been the single most
important social nexus ....>>

Does he mean "single" = "very"? I doubt it, but if he does "very" (or
nothing) would be preferable IMHO.

I think he means that of an imagined group of nexuses (maybe "military;
mining; colleges; farming; churches; ....") the military nexus is the most
important *single* one -- leaving open the possibility of defining (e.g.) a
composite "civilian" nexus which would outweigh the military one. That is,
I think "single most important" here means exactly "most important single".

Most of us would not casually replace, say, "the largest fresh-water lake"
with "the fresh-water largest lake". So why is (e.g.) "the single largest
contributor" apparently often thought to be a good way to say "the largest
single contributor"?

Or am I missing something (again)?

-- Doug Wilson