'reductant' originates from the Latin word 'reducere,' where 're-' meant 'back' and 'ducere' meant 'to lead.'

'reducere' transformed into the French word 'réduire,' and eventually became the modern English word 'reduce,' from which 'reductant' is derived.

Initially, it meant 'to lead back,' but over time it evolved into its current meaning of 'a substance that donates electrons.'