'nitrogenous' originates from the word 'nitrogen', which is derived from the French word 'nitrogène', where 'nitro-' referred to 'niter' and '-gène' meant 'producing'.

'nitrogène' transformed into the English word 'nitrogen', and eventually the adjective form 'nitrogenous' was derived.

Initially, it meant 'producing niter', but over time it evolved into its current meaning of 'containing nitrogen'.