The term "Nitrox" was originally coined to describe a breathing gas used for shallow saturation diving in underwater habitats. The breathing gas was basically air, with a decreased oxygen level. This oxygen reduced gas, "nitrox" was necessary for the long-term storage of divers in shallow saturation. The oxygen level in (normoxic) air would eventually cause lung damage (pulmonary oxygen toxicity) at the increased saturation pressure.

When divers started adding oxygen to air, to extend their bottom times, they called it "enriched air nitrox". Eventually, this phrase was shortened to just "nitrox". Although it is inaccurate, it is generally accepted by divers to mean Oxygen Enriched Air,  or OEA.

As working divers, we correctly refer to oxygen reduced air as "nitrox" for use in shallow saturation, and "enriched air nitrox" or "oxygen enriched air" for air that has oxygen added.