'guideline' originates from the combination of 'guide' and 'line', where 'guide' meant 'to lead or direct' and 'line' referred to a 'path or boundary'.

'guideline' evolved from the Middle English word 'guydelin', which was a combination of 'guide' and 'line', eventually becoming the modern English word 'guideline'.

Initially, it meant 'a line that guides', but over time it evolved into its current meaning of 'a rule or principle'.