There's a graph that's been going around this week, showing how Americans have gotten more foul-mouthed over the past quarter-century or so:

It appeared on Vox on Tuesday, as part of an explainer titled "5 surprising things scientists have discovered about swearing." None of those five things should be the least bit surprising to anyone who is even semi-neurotypical and vaguely literate ("Swearing can be socially useful—but can also backfire." Wow, no fucking shit).

But the rather obvious premise behind the graph—"Swearing seems to be getting more common over time"—might not be as simple as it appears. We all know the basic story: The Baby Boom was born, and as it grew up it invented many things unavailable to its preceding generations, including not just oral sex and marijuana, but the word "motherfucker." Old prudish standards of behavior went out the window, and now everyone calls everyone else "cocksucker" all the time, or "cggksggkk" if they are trying to say it while simultaneously holding a real live cock in their own mouth, as most people usually are.

So the graph records a study in which researchers asked American adults "to rigorously record every time they heard a swear word in public for an entire year" and compared the results to an earlier study. Vox also included a Google ngram chart of word frequencies in published works, which shows "shit" and "fuck" rising from essentially zero in 1950 into common use today, while "damn" follows a similar slope just above them. Gosh!

And yet: "gosh." Here's another Google ngram, addressing a question about bad language that Vox did not:

Yes, starting in 1950, "motherfucker" goes from being completely absent in Google's corpus of published American English to rocket past a whole batch of stodgy old-fashioned substitutes for swear words. And then, in the early 1970's...some of those words start rising in frequency right along with it.

From about 1975 to the present, whatever force carried "motherfucker" up the chart seems to have been acting at the same rate as the force carrying "gosh" and "dang." Even more striking is "heck," which after almost being caught by "motherfucker" went off on a trajectory more suitable for a rock star than for its fellow mild exclamations.

What in the blazes really did happen?