Regarding the origin of "fork-tailed devil", it is incorrect to think that Caidin invented it, and a little more detail on this mistaken perception is a good reason why you shouldn't put much weight in "I didn't see it anywhere else, so it probably isn't true."
I, too, have read German-authored books (and non-German-authored books that are very finely detailed, such as to daily diary levels, such as JG26: Top Guns of the Luftwaffe) and haven't seen "gabelschwanz teufel". That is not a negative proof.
I have read accounts from pilots (The Wrong Stuff, by Smith, a B-17 pilot, and Malta's Greater Siege, by Warburton, P-38 pilot, for example) who, in writing about it, say it was called the "fork-tailed devil". But they might have picked it up from parlance post WWII and assumed it was a term used during WWII. In his book, Warburton says that he used "Gabelschwanz Teufel" while he was flying it in WWII. Maybe he misremembered, though -- it is possible.
Interestingly, though, there is this from Lockheed's corporate site (
http://www.lockheedmartin.com/us/100years/stories/p-38.html ):
"Within six months, as the P-38 showed its versatility in North Africa, a lone hysterical German pilot surrendered to soldiers at an Allied camp near Tunisia, pointing up to the sky and repeating one phrase—“der Gableschwanz Teufl”—over and over. Once the phrase was translated, U.S. officials realized the focus of the pilot’s madness. The P-38 had been given a new nickname: the “fork-tailed devil.”"
The details of that account do not appear in Caidin's Fork-Tailed Devil. Caidin's book mentions the term "fork-tailed devil" only once in the whole book, in chapter 8, where it says: "NORTH AFRICA WAS WHERE the P-38 earned its name— Der gabelschwanz teufel. The fork-tailed devil. It took a while, though." That's all it says. Details mentioned in the Lockheed article don't appear in Caiden's book, and so it seems unlikely that Caidin is the source of those extra details.
The Lockheed article lists these as its sources:
-- Boyne, Walter. Beyond the Horizons: The Lockheed Story. New York: St. Martin’s Griffin, 1999.
-- Pace, Steve. Lockheed P-38 Lightning. Minneapolis, MN: Motorbooks International Publishers and Wholesalers, 1996.
-- Stanaway, John. P-38 Lightning Aces of the ETO/MTO. Oxford, UK: Osprey Publishing, 1998.
-- Gray, William P. “P-38” Life magazine, 16 August 1943.
It would be most interesting if the 1943 Life Magazine article were the source, of course.
As it turns out, from Life Magazine, 1943, in the article "P-38" (
https://books.google.com/books?id=RVAEAAAAMBAJ&lpg=PA51&dq=gabelschwanz%20teufel&pg=PA51#v=onepage&q=gabelschwanz%20teufel&f=false )
"Into that camp the military police brought a disheveled German flier who was mumbling hysterically and repeating something about 'der Gabelschwanz Teufel'. An interpreter was called, and he had the translation quickly: 'the fork-tailed devil'. The German was talking about the P-38."
So, there you have it.
Either a German pilot did originate the term "fork-tailed devil", or Life Magazine made it up in 1943 for one of their articles.
Either way, Caidin is not a liar about that term.
