The "F-word" in N-gram Viewer

Did you check any of your Ngram results? The early hits are mostly false drops from typographical and OCR considerations, so the tail on the distribution continues to the left. Prudishness and censorship combined to make it ʃucking impossible to get the word published until "modern" times. Now no one cares about the word when the internet is dedicated to videos of the act.

It looks like what Andrew Leach and deadrat pointed out are very keen observations. I checked about 50 links of books before 1820 times, but nowhere have I found the word "fuck" (almost everywhere it is a misreference of Long S (f without the crossbar) , as in ſuck (suck), ſucked (sucked), ſuck'd (suck'd), ſucking(sucking) and other variations). This explains why the anomalous graph went above sea level before 1820.

^{Screen shot from The Dramatic Works of Shakspeare: In Six Volumes, Volume 3, Clarendon Press, 1789.}

It seems like "fuck" is a pretty modern word not much used by the writers of 18th and early 19th century (even though Wikipedia says its first accepted usage was registered on the 15th century). This modernness can be demonstrated with N-gram if I replace "fuck" with "Fuck" and we can see the bold green bar erasing the apparent aberration.

NOTE : Declaring "fuck" as a pretty modern word is purely based on pieces of evidence provided by the N-gram graphs whose corpus includes only the uploaded published text to google books. So chances are there that this can be a tentative declaration. But still we can get partially the idea of its very modernness in prints.