That is a fictional character in the novel Cryptonomicon by Neal Stephenson.
Moreover, the action of the novel is in WWII, many years after the public disclosure of the one-time pad by Vernam, which happened in 1926.
While the novel Cryptonomicon uses the term "one-time pad", it is very likely that this is an anachronism, because I have not seen any document from WWII or earlier that uses this term. The classified manuals of Military Cryptography and Military Cryptanalysis written by Friedman described it without using a special term for it, while Shannon, in 1945 and 1949 called it the "Vernam system", quoting the only non-classified source for it, i.e. the paper written by Vernam. I believe that the term "one-time pad" might have been coined during the Cold War to describe the ciphers used by Russian spies, who used random keys written on sheets of paper, which were destroyed after use. So in the beginning it was not a term referring to ciphers implemented by machines.
Before the classified work of Friedman from 1918, who cryptanalyzed documents intercepted in France in the final months of WWI, there was a certain Frank Miller who has described a kind of one-time pad in 1882.
However, what Frank Miller has written did not have any influence on cryptology. Moreover, his choice appears to have been just a lucky guess, which was not based on any experience in breaking ciphers or on any mathematical theory.
Leo Marks' memoirs, _Betweek Silk and Cyanide: A Codemaker's War, 1941-1945_ about his time as chief cryptographer of SOE, frequently discusses two major ideas of his that he pushed regularly: Worked Out Keys (WOKs) and Letter One-time Pads (LOPs). His heavy use of that acronym in his book written in 1998 is pretty strong evidence to me that he at least used that term of art during the war. Now, at least as presented in his memoirs, he was mostly isolated from the main cryptographic efforts of the war, so it seems unlikely that e.g. Meredith Gardner and the Venona Project would have encountered his use of the term, so I think that strongly suggests that the term pre-dates WW2 unless it was a simultaneous coinage.
That would make "one-time pad" a British term, which is consistent with the non-existence of this term in the early American documents.
Even if "one-time pad" had been used by the British during WWII, that would still make its use in Cryptonomicon inappropriate, because there it was used by an American.
Thanks for pointing to Leo Marks' book. I have just browsed it and it is weird how unfamiliar he was with the previous cryptographic literature, despite being a trained cryptographer.
According to his memoirs, Leo Marks had great difficulties in rediscovering the "letter one-time pads", in order to replace the "digit one-time pads", which were inconvenient for Morse transmission.
Not only the solution to his problem was clearly explained in Vernam's article from 1926, which had been published in both the Transactions of the A.I.E.E and in the Journal of the A.I.E.E, which were journals important enough to be available in various British libraries, but the solution searched by him was also explained in various popular publications, even in one of the novels written by Jules Verne almost a century earlier.
Anyone familiar with the history of cryptography and with the various kinds of ciphers used in the past would have thought instantaneously to the correct solution for implementing the desired "letter one-time pad" (i.e. by addition modulo 26 of the numerical positions of the letters in the alphabet). Also, had they been well aware that good one-time pads are unbreakable, they should have easily realized that the double encryption with a codebook followed by a one-time pad is useless.
From his memoirs, it appears that his knowledge of cryptography, at least in the initial part of WWII, was much inferior to the content of the manuals written by Friedman, which were used for training the American cryptographers, although it appears that in time, after gaining experience, he has become good enough.
As he presents himself in the book, at least, he was basically a dilettante, one of many who got sent to the GC&CS at Bletchley (the people who get described in Kahn 1991 or Winterbotham or Calvorcessi in their explanations of who worked at Hut 6 or 8 as 'linguists, mathematicians, people who wrote crossword puzzles' types). He flunked out of GC&CS, however, and only got the job with SOE by the skin of his teeth (the general in charge of SOE wanted him to decrypt an actual operational message but forgot to give him the key- the general wanted to see how fast he was at doing the double transposition cipher compared to a clerk, but instead Marks over the course of a day's work cracked the actually sent operational message without the key, which impressed/scared the general far more and got him the job).
But he had just rapid wartime training of learning by doing, and he was largely by himself as the only cryptographer in SOE, at least as he depicts it, so it highly plausible to me that he missed a lot of things that were widely known in the broader cryptography community. (It was because he was so isolated from the rest of the British crypto community that he ended up allowed to write public memoirs, I suspect. Wiki says he wrote it in the early 1980's and wasn't allowed to publish until 1998.)
