'gratis' originates from Latin, specifically the word 'grātīs', where 'grātia' meant 'favor' or 'kindness'.

'grātīs' changed from the Latin word 'grātia' and eventually became the modern English word 'gratis'.

Initially, it meant 'by favor' or 'as a kindness', but over time it evolved into its current meaning of 'free of charge'.