Wordorigins.org

Nitrogen, the element with atomic number 7, takes its name from the French nitrogène. The root nitro- is a combining form of the nitre, via French from the Latin and Greek nitrum. Ultimately, it may come from the Egyptian ntrj. Nitre is a name for a variety of chemicals, including sodium carbonate (soda) and potassium nitrate (saltpeter).¹ Nitrogen uses this root because it was first isolated from solutions of nitric acid.