'touchstone' originates from Middle English, specifically the word 'touche-ston,' where 'touche' meant 'to test' and 'ston' meant 'stone.'

'touche-ston' transformed into the modern English word 'touchstone.'

Initially, it meant 'a stone used to test the purity of gold or silver,' but over time it evolved into its current meaning of 'a standard or criterion.'