Diving

La narcose à l’azote and l’azote résiduel both turn on a word that English looked at and refused. L’azote is nitrogen, and the name is a judgement rather than a description. It was built out of Greek, from the privative a- and zōē, life, and it means the gas that will not keep an animal alive: take the oxygen out of air and what remains puts a mouse out. Lavoisier and the chemists around him settled on it while the new naming of the elements was being written. A rival term came out of the same school a few years later, nitrogène, the gas that makes nitre, and English took that one and wore it down to « nitrogen ». So both names were coined in French, and each language kept the one the other let go. The older root did not leave English entirely: it survives in « azo dyes » and in « azide », where the chemistry remembers the Greek that the everyday word has forgotten. For a diver the French name is the more useful of the two. Nothing in « nitrogen » says anything at all; azote says that this gas is not the one keeping you alive.