[celticjames]

Multiple meanings for 'tits' are also a consideration. (Maybe my monitor or eyes suck, but I had to do a tits vs fuck only ngram search to see that the big spike is in fact tits.)

[gjm11]

I think either your monitor or your eyes must in fact fu- I mean suck, because the big bulge (it's not exactly a spike) is for "fuck", not for "tits".

(And most of it does in fact seem to be for wrongly-OCRed "suck", unsurprisingly.)

[pavel_lishin]

Note the long-s discussion earlier in this submission.

Maybe life just really fucked back then.

[nzmsv]

Yes, a quick look at the actual search hits shows that most of these books are in fact about birds, and a couple hits are citations and refer to a last name.