Recrudescence is the revival of material or behavior that had previously been stabilized, settled, or diminished. In medicine, it is the recurrence of symptoms in a patient whose blood stream infection has previously been at such a low level as not to be clinically demonstrable or cause symptoms, or the reappearance of a disease after it has been quiescent.
I’ve run across this word in a couple of books lately (the most latest is The Plague by Albert Camus, and the previous occasion might have been The Undiscovered Self by C.G. Jung).
So maybe I should remember it since it’s very popular in the middle of the 20th century amongst intellectuals.