Nostalgia has an air of total irreconcilability. There is the feeling the word describes, of course: a fundamentally impossible yearning, a longing to go back even as we are driven ceaselessly forward, pushed further away from our desire even as we sit contemplating it. But it''s the actual feeling, too, that ceaselessly resists any attempt to give it shape or sense. If we say we feel nostalgic, in general or about something in particular, it rarely needs an explanation, and there likely isn''t a good one anyway: Why should it be the smell of our grandmother''s cookies or the feel of a particular sweater or the sight of a certain tree in a certain playground, and not something else, that sends us searching backwards? Why is it welling up now, on an otherwise unremarkable Tuesday? Why haven''t I felt this way for a long time? Why does it matter? And that assumes it even occurs to us to interrogate this sudden rush: one of nostalgia''s more persistent qualities is its ability to elide reason, to be felt deeply without prompting any further inquiry. It''s this strange aura of elusive profundity that makes nostalgia seem less like some sort of modern condition than a universal feeling that took us some time to put our finger on. If feelings in general are internal experiences that demand expression whether or not we have the means for it, our inability to actually do anything with nostalgia might be what kept it ineffable for so long. Most kinds of longing can be settled in one way or another, if not necessarily to the satisfaction of the yearner. Nostalgia can only be lived in or abandoned: it is yearning distilled to its essence, yearning not really for its own sake but because there is nothing else to be done.

Maybe it resisted definition so long because naming it doesn''t help resolve anything anyway. Appropriately for the elusiveness of the concept, the word nostalgia did not originally mean what we now consider it to -- also appropriately, it was coined with a longing for a time when there was no word for what it described. Specifically: in 1688, a Swiss medical student named Johannes Hofer gave the name nostalgia to a malady he had noticed in young Swiss people who had been sent abroad -- chiefly mercenaries, one of Switzerland''s prime exports at the time, though also household servants and others who found themselves in "foreign regions." As was the style at the time in the nascent field of "medicine more complicated than bleeding humours," Hofer used a portmanteau from an indistinctly highfalutin form of Ancient Greek: nostos roughly means "home" -- although it more often means "homecoming," which incidentally was also the name for an entire subcategory of Greek literature, most notably the Odyssey -- while algos means, more simply, "pain," derived from Algea, the personifications of sorrow and grief, and a common classification at the time, attached to a variety of maladies that have since gotten either more precise or more vernacular names. (If you ever want to stoke excessive sympathy from, say, your boss, tell them you have cephalgia or myalgia -- a headache or sore muscles, respectively). So nostalgia literally means "pain associated with home" -- or in slightly more familiar terms, "homesickness." This is not a coincidence, but more relevantly, it''s also not a case of fancy medical-speak being dumbed down for popular consumption. At least not generally: the English word homesickness is a more or less direct translation of nostalgia .

But the original term is French, maladie du pays , and not only does it specifically refer to the tendency of the Swiss to powerfully miss their home country, it precedes Hofer by at least thirty years. Hofer''s coinage brought a specifically medical dimension, insomuch as medicine as we know it existed in his time: Hofer''s observations were quite detailed, but still entirely anecdotal, and subject to a lot of conjecture. What he lacked in scientific rigour he made up for with linguistics, attempting to legitimize medicine''s dominion over the concept with multiple coinages, including nostomania (obsession with home, which, as you''ll see in a second, is probably more accurate to the "disease" as he conceived it), philopatridomania (obsessive love of one''s homeland), and years later, in the second edition of his thesis, pothopatridalgia (pain from the longing for the home of one''s fathers, which certainly has the advantage of precision, if not rhythm). Though the difference between mere homesickness and medical nostalgia was mostly a case of ancient language, Hofer nevertheless describes a serious disease, one that could progress from simple physical ailments like ringing in the ears or indigestion to near-catatonia and even death. Its root cause, according to Hofer, was "the quite continuous vibration of animal spirits through those fibres of the middle brain in which impressed traces of ideas of the fatherland still cling." As Helmut Illbruck explains in his book Nostalgia: Origins and Ends of an Unenlightened Disease , essentially what that means is that the nostalgic suffers from a powerful obsession with their home that eventually makes them entirely insensate to any other experience or stimulation. Illbruck points out that the action Hofer describes does loosely capture how the brain seems to store, process, and recall memories, which may explain some of why his concept caught on, at least in the medical circles in which it persisted for the next few hundred years. As it happens, though, a primordial understanding of the structure of the mind isn''t the only key insight that would stick to nostalgia even as its conception developed.

There are two other big ones. First, Hofer recognized that nostalgia was less about whatever the nostalgic claimed to be missing than about "the strength of the imagination alone": it seemed to have less to do with any material differences in the patient''s circumstances than with the collective weight of their memories, even though those were centred on a very real and specific place. Hofer''s final, curiously potent observation is his suggested cure, which he meant quite sincerely, but which elegantly captures the futility of trying to tame nostalgia, disease or otherwise: "Nostalgia admits no remedy other than a return to the Homeland." In all his observations and diagnoses, Hofer does not seem to fully appreciate that home is often more time than place. The proof of this will reveal itself as nostalgia evolves into something so incurable that it stops being a disease entirely, and its longing begins to be associated specifically with times past -- but we are getting slightly ahead of ourselves. Doctors proceeded to speculate about the causes and potential cures of nostalgia until roughly the twentieth century, often ignoring Hofer''s observation about the imagination''s effects, causing some curious mutations in the idea. Nostalgia did remain almost the exclusive province of the Swiss for the first few hundred years after its naming -- one of the original German words for homesickness, in fact, was Schweizerkrankheit , or "the Swiss illness." Hofer''s near-contemporary Johann Jakob Scheuchzer -- a Swiss naturalist who was chiefly interested in rescuing his countrymen''s reputation from accusations of weakness -- suggested that it was the change in air pressure (and maybe even quality) that made them so prone to debilitating longing.

He suggested that a brief stay at the top of a tower or on a hill might restore some of their strength. There isn''t much proof Scheuchzer''s conception of the disease or cure ever really worked, but there is some indication that this sort of thinking is where Switzerland got its reputation as a healthful place to recover in a sanatorium or spa. Well after Scheuchzer, eighteenth-century physicians spent some time looking for a physical locus for nostalgia -- a specific brain structure or bone -- which was just as futile, with even less of an impact on Swiss tourism. Gradually, the notion of nostalgia attached itself almost exclusively to soldiers -- Swiss mercenaries being very popular hires in armies across the continent, and doctors being a regular part of army life. It would take a little more than two centuries for doctors to figure out that there might be something more than a mysterious nerve disorder causing young men whose sole job was dismembering other humans and dying gruesomely to yearn for the comforts of home; in the meantime, cures and coping methods grew a little more creative. There are stories, including one from Jean-Jacques Rousseau''s Dictionnaire de musique , of foreign officers banning the playing of Swiss Ranz-des-Vaches -- cow-based folk songs, historically played by herdsmen on horns as they drove their cattle down from the mountain pastures -- and even the sound of cowbells, lest it paralyze their troops in nostalgic reverie. (It became a tenet of folk wisdom about the Swiss that the Ranz-des-Vaches had this power over them; it featured as metaphor or plot point in eighteenth- and nineteenth-century philosophical dialogues, dramas, poems and operas, particularly by German Romantics, who were constitutionally interested in a disease that spoke so acutely to our conceptions of self.) By the 1800s, the terrors of nostalgia finally spread to other countries'' soldiers.

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