'two-stage' originates from the combination of the words 'two' and 'stage', where 'two' signifies the number 2 and 'stage' refers to a phase or step in a process.

The term 'two-stage' has been used in various technical and scientific contexts to describe processes or systems that operate in two distinct phases.

Initially, it meant 'involving two steps', and this meaning has largely remained the same in modern usage.