A new search capability has been introduced by Google that allows you to graph search results across a deep archive of digitized books. In the version currently available you can go back to 1500.
Graphing interest in “British English” for Heidegger and Foucault gives the following.
Pretty strong continued interest, especially since the 1990s. But if you look at “American English” books you see more of a downturn.
And overall this is more marked.
Going in to more detail shows the picture isn’t quite as clear. Maybe it’s better to think of cycles of interest.
Try your own name (and then try it against somebody famous to come down to earth!). I tried my own name, which showed increasing hits (yay!), but then against David Harvey I was basically bumping along the x-axis as the scale changed….