A compound made up of nostos, meaning “journey” or “journey home,” and algia, “pain,” nostalgia is not and simply could not be a Greek word. In compounds like kephalalgia (headache) or glossalgia (a pain in the tongue, or mouthiness), it is the modifier’s function to pinpoint where exactly the rather precise pain is felt and situated. Nostalgia readily suggests the pain caused by the longing for home, yet it identifies no bodily part. Of what nature is the pain, then, and where could it be located?

Helmut Illbruck, Nostalgia: Origins and Ends of an Unenlightened Disease