incestuous = 'objectionably reciprocal in social or intellectual terms'

[Jonathan Lighter]

Right, everybody knows this.  Unfortunately, OED places it vaguely, with no
def., under 2c "Fig." with an 1869 from D.G.Rosetti, where the metaphor of
real incest is explicit - but not another till 1971, when the current nuance
is full-blown.

Here's a big gap-filler:

1943 James Agee in _The Nation_ (July 17) 82:  [T]he difficult question of
the proper and the incestuous relationship, in any work of art or
entertainment, between nature and artifice.

I mean, where's the "incest"?

JL

--
"If the truth is half as bad as I think it is, you can't handle the truth."

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