'sleeplessness' originates from Old English, specifically the word 'slǣpan,' where 'slǣp' meant 'sleep' and the suffix '-less' indicated 'without.'

'slǣpan' transformed into the Middle English word 'slepen,' and eventually became the modern English word 'sleep,' with 'sleeplessness' forming by adding the suffix '-ness' to 'sleepless.'

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