'energy-saver' originates from the combination of 'energy' and 'saver', where 'energy' refers to the capacity for doing work and 'saver' implies something that conserves or reduces usage.

'energy-saver' evolved from the increasing need to conserve energy in modern times, particularly with the rise of environmental awareness.

Initially, it referred to any method of saving energy, but now it often specifically refers to devices designed to reduce energy consumption.