So his theme cropped up after that last episode…
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Having looked through historic googlebooks many a time and been frustrated by how difficult it is to search in this time period, this chart is most certainly due to the algorithm not properly picking up the "Long S" which was an f-like character used in place of an s especially in 17th and 18th century printing.
The rules of when the short and long s's are used are somewhat complicated to modern people, but they are almost always at the beginning of words, never at the end, and if there is a double s sometimes they are combined and sometimes not:
99% of the time the word actually being used is "suck" or "sucking." It actually shows up a lot as a word used to describe babies who were still nursing. In texts from this period the word "suck" will almost always read as "fuck." This makes some of these auto-transcriptions absolutely brilliant in hindsight:

If you search for the word "fuck" in googlebooks within this time frame, you get hundreds of pages of entries like this. For example, this Shakespeare anthology:
This is not to say that people in the 18th century didn't find this hilarious, I'm sure they did, but f-bombs were not being dropped in classic literature at the time. If they do show up, like in this 1785 slang dictionary: it is almost always bleeped out:
The other 1% of the fucks in 18th century books are, of course, not bleeped out because they are in Ye Olde Porn, of which there is a surprising amount on googlebooks.
I should also note if it wasn't clear that the immense dropoff just after 1800 is when the long s stopped being used in print, and the reemergence was in the mid-late 20th century when people DID start dropping f-bombs in literature














