Interpreter of Maladies is the title of one of the stories in the book. And the phrase itself was something I thought of before I even wrote that story.
Once I have a hook I think has potential - enough to spin out more than a hundred thousand words, then I start turning my attention to characters. Who are these people? Why did this thing happen to them? But the hook always comes first.
For in 1900 all electromagnetic radiation of longer wavelengths was already known at least to the extent that one could not seek in it the more striking characteristics of X-rays such as, for example, the strong penetrating power.