It goes back a bit further than that. His 1948 “Mathematical theory of communication” [1] already has (what we would now call) a Markov chain language model, page 7 onwards. AFAIK, this was based on his classified WWII work so it was probably a few years older than that
reply[1] https://people.math.harvard.edu/~ctm/home/text/others/shanno...
I was just reading Norbert Wiener's "The Human Use of Human Beings" (1950) and this quote gave me a good chuckle:
reply"One may get a remarkable semblance of a language like English by taking a sequence of words, or pairs of words, or triads of words, according to the statistical frequency with which they occur in the language, and the gibberish thus obtained will have a remarkably persuasive similarity to good English."
A letter is not a token, is it? Redundancy could hit 75% in long sentences, but Shannon was not predicting tokens or words, he was predicting letters (characters).
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