In the age of coronavirus and COVID-19, comparisons are being made to an unusually long-lived and virulent  epidemic of influenza that occurred a century ago. The so-called "Spanish" flu went around the world in three waves, claiming more than fifty million lives--more than perished in the just-ended First World War. What was the Spanish flu? Why was it called that? And can we learn anything about what's in store during the coronavirus pandemic of 2019-20 by casting our eyes back a century?