@joeyh I've read elsewhere that Google's Ngrams (and book scanning) is heavily skewed toward academic publishing from roughly 1920 -- 1990 or so. It's a combination of books falling into the copyright hole, emphasis on academic corpora (e.g., University of Michigan) as major contributors to the scanning project, and the emergence of digital book formats in the very late 20th century.
Douglas Harper of The Online Etymological Dictionary addresses this in a blog post:
https://www.etymonline.com/columns/post/who-lusts-for-certainty-lusts-for-lies
