Thanks to all for your answers to my query, particulary Robert Boyle, who of course got it from the source. (By the way, the word VN used was "wonderful," not "delightful," as I had remembered it.) Since posting my query, I did find one high-profile instance where "red wop" clearly refers to wine. In Truman Capote's In Cold Blood, we find the following:
"So I found a liquor store and bought a half gallon of red wop and went back to the bus depot and sat there drinking my wine..." (Vintage, pg. 137)
See it here:
This was written after PF, but in roughly the same time period, so it seems pretty clear that some people would have understood the term as referring to wine. It's interesting that VN used the term in his letter to Wilson, in his interview with Robert Boyle, and in PF without feeling the need to explain what the term meant. He seemed to think the meaning was well-known. Perhaps it was one of those slang terms that, while common enough, rarely made it into print. Proof, I suppose, that the written record of an age cannot very accurately reflect way people actually communicated on a daily basis.
>>> On 2/19/2010 at 12:16 AM, in message <firstname.lastname@example.org>, "Robert H. Boyle" <KatyaBelousBoyle@AOL.COM> wrote:
To answer Matt Roth's query about the meaning of "red wop." It has nothing at all to do with red wine. From the way VN expressed it to me, he obviously meant an Italian with a red face. Now to the etymology of "wop." .
In 1976 Mrs. Carl (Mary Josephine) D'Alvia of Croton-on-Hudson, NY, published a book, The History of the New Croton Dam, an enormous structure completed in the early 20th century to add to New York City's water supply. It was built by stone-cutters and masons brought over from Italy by a padrone.. When the immigrants got off the boat, as Mrs. D'Alvia notes on page 97, the padrone handed each of them $25 because they landed "with out passage" money, abbreviated "W. O..P." and soon the pejorative "wop" for an Italian.
Robert H. Boyle .