Oxygen Was Almost Named Nitrogen.

In his Tractatus Quinque Medico-Physici of 1674, John Mayow wrote that a fifth of atmospheric air is comprised of nitro-aerial spirit. That so-called spirit participates in both respiration and combustion. The etymology of "nitro-aerial spirit" stems from a mineral long called niter and now specified as potassium nitrate. Niter mixed with sulfur and carbon is gunpowder, developed in the ninth century in China. Mayow appreciated that niter was the oxidant in the energy-yielding reaction of gunpowder. The word "oxygen," eventually prompting the word oxidant, was coined a century later by Antoine Lavoisier.