influenza

In Italian, influenza means 'influence'—from Latin influere, 'to flow in.' When a mysterious illness swept through Italian cities in the Renaissance, people attributed it to the influenza of the stars—the malign astrological influence that caused epidemics. The stars flowed their sickness down upon you.

The concept made sense in a pre-germ-theory world. Epidemics appeared suddenly, struck everyone at once, and disappeared just as quickly. What other force could affect an entire population simultaneously except the alignment of celestial bodies? Individual illness had individual causes, but mass illness required a cosmic explanation.

English borrowed influenza in 1743 during a major European epidemic. The Italian word was adopted wholesale, complete with its astrological superstition. English speakers shortened it to flu by the 1830s—four syllables reduced to one, and all the celestial poetry evaporated.

The 1918 influenza pandemic killed an estimated 50-100 million people—more than World War I. The word that blamed the stars for illness was now naming the deadliest pandemic in modern history. We know now that influenza is caused by orthomyxoviruses, not stars. But the word remembers a time when the only explanation for mass suffering was that the heavens were against you.