hydrogène

The Greek roots are hydor (ὕδωρ), meaning 'water,' and genes (γενής), meaning 'producing' or 'born of.' But nobody in ancient Greece named this element. It took until the 1760s for Henry Cavendish to isolate what he called 'inflammable air' — a gas that burned with a pale blue flame and left behind droplets of moisture. Cavendish did not name it. He was too cautious for that.

Antoine Lavoisier, the French chemist who dismantled phlogiston theory and rewrote chemistry's language, gave the element its name in 1783. He called it hydrogène — 'water-former' — because burning it produced water. This was Lavoisier's method: name elements by what they do, not by what they look like. He was building a rational nomenclature from scratch, and hydrogen was his first brick.

Lavoisier did not live to see what hydrogen would become. The Revolution that inspired the metric system also consumed its architects. Lavoisier was guillotined on May 8, 1794. The mathematician Lagrange said afterward, 'It took them only an instant to cut off his head, and one hundred years might not suffice to reproduce its like.' The man who named water's parent was killed by the state he had served.

Hydrogen is the first element on the periodic table, the fuel of stars, and the most abundant substance in the observable universe. Every drop of water, every living cell, every star burning in every galaxy runs on hydrogen. Lavoisier's word — water-former — turned out to be the understatement of all time. Hydrogen does not merely form water. It forms everything.