'anaesthesia' originates from Greek, specifically the word 'anaisthēsia,' where 'an-' meant 'without' and 'aisthēsis' meant 'sensation.'

'anaisthēsia' was adopted into Latin as 'anaesthesia,' and eventually became the modern English word 'anaesthesia.'

Initially, it meant 'lack of sensation,' and this meaning has remained consistent in modern medical usage.