The Online Etymology Dictionary entry for the verb to approach references propinquity (NED, psychology, AHD, wiktionary) which contains a reference to an aphorism:
late 14c., "nearness in relation, kinship," later also "physical
nearness" (early 15c.), from Old French propinquite (13c.) and
directly from Latin propinquitatem (nominative propinquitas)
"nearness, vicinity; relationship, affinity," from propinquus "near,
neighboring," from prope "near" (enlarged from PIE *pro "before;"
see pro-) + suffix -inquus.Nothing propinks like propinquity [Ian Fleming, chapter heading, "Diamonds are Forever," 1956; phrase popularized 1960s by U.S.
diplomat George Ball ][ Online Etymology Dictionary – n.b. added links ]
He often used the aphorism (perhaps originally coined by Ian Fleming
in Diamonds are Forever) "Nothing propinks like propinquity," later
dubbed the Ball Rule of Power. It means that the more direct
access you have to the president, the greater your power, no matter
what your title actually is.[Wikipedia @ George Ball, note omitted]
On Books the Diamonds are Forever can be found (such as here with the cover of The Diamonds Smugglers, which is Mr Fleming's non-fiction work from the research for the novel); in it, there is the aforementioned heading. When you scroll a few pages down, you have the following:
[Felix]Leiter Chuckled. "Come on lovebirds," he said, looking at his
watch. We ought to get going. I've got to get back to Vegas tonight
and start looking at the skeleton of our dear dumb friend Shy Smile.
And you've got your 'plane to catch. You can go one quarreling at
twenty thousand feet. Get a better perspective from there. May even
decide to make up and be friends. You know what they say" – he
beckoned to the waiter – "nothing propinks like propinquity."
[…]
Bond knew that he was very near to being in love with this
girl.[…][Ian Fleming, Diamonds are Forever, 26 March 1956/UK]
I don't know the novels, but Felix making some sort of insinuation is not necessarily out of character from what I remember of the movies; I construe the reference as such. But for a U.S. diplomat of the (President)Eisenhower era to be using exactly that and then having the Ball Rule of Power being coined after it strikes me as somewhat odd. Or is it?
Who came up with "nothing propinks like propinquity" (if not for Mr Fleming); is that "heading" from the novel really the basis for Mr Ball using it and for the Ball Rule of Power being coined?
Best Answer
It looks to me as though Ian Fleming is the first author to have used the expression, "Nothing propinks like propinquity." A Google Books search for propinks strikes out on anything older than 1956, as does a Library of Congress newspaper search for the word propinks across the period 1836–1922.
The online attributions to P.G. Wodehouse seem based on a conversation in Right Ho, Jeeves in which Jeeves suggests propinquity as the word Bertie Wooster is trying to think of, and Bertie confirms that it is. (The conversation appears on the Association of Independent Librarians page that Hot Licks links to in a comment above.) None of the online attributions of the quotation "Nothing propinks like propinquity" either to Wodehouse or to Dorothy Parker that a Google Books search turns up identify a page in the author's work where the expression appears. This is a warning sign (though not a definitive proof in the negative) of false attribution.
The only quotations involving propinquity that make their way into The Oxford Book of Quotations, third edition (1979) are from Shakespeare, King Lear:
and from Mrs. Humphrey Ward, Robert Elsmere (1888):
The quote from Robert Elsmere has much in common with "Nothing propinks..." as an idea, but I don't think that Ian Fleming owes her any royalties on the wording he devised.