'pitiless' originates from Middle English, specifically the word 'pitiles,' where 'pite' meant 'pity' and '-les' meant 'without.'

'pitiles' transformed into the modern English word 'pitiless' by dropping the 'e' and adding '-ness' to form 'pitilessness.'

Initially, it meant 'without pity,' and this meaning has largely remained the same in modern usage.