An archaic word for nitrogen. May be encountered in works of steampunk.
In 1772 Daniel Rutherford discovered that you could isolate.... something from air; specifically, a gas that suppressed combustion, and yet was not "fixed air" (AKA carbon dioxide).
In 1774 Joseph Priestley discovered that you could isolate.... something else from air; a gas that increased combustion.
Further experiments showed that animals could not live for long in jars filled with the first gas. But if put in a jar filled with the second, they would be friskier than usual. (Joseph Priestley reported that after breathing in this second gas he felt "light and easy".) The French chemist Antoine Laurent Lavoisier put these bits of information together, and concluded that air was composed of two separate substances; one-fifth Priestley's gas, and four-fifths Rutherford's gas.
He went so far as to name them. The one that encourages combustion he named 'oxygen', from the Greek words meaning 'acid-producer' (he believed, incorrectly, that all acids contained this substance). The one that does not permit combustion he named 'azote', from the Greek words meaning 'no life'. These results also caused him to equate life with a form of slow burning.
Azote was (re)named nitrogen in 1790 by J. A. Chaptal, because it could be produced from the mineral niter. Oxygen was not renamed. I find this ironic.
The French language still uses azote to mean nitrogen, and uses AZ for the atomic symbol.
For what it's worth, azote also means 'scourge' in Spanish.