'easy-to-understand' originates from the combination of 'easy' and 'understand', where 'easy' meant 'not difficult' and 'understand' meant 'grasp the meaning of'.

'easy-to-understand' evolved from the phrase 'easy to be understood' in Middle English, eventually becoming the modern English adjective 'easy-to-understand'.

Initially, it meant 'simple to grasp', and this meaning has largely remained the same in modern usage.