'anaesthetically' originates from English, specifically from the word 'anaesthetic' with the adverbial suffix '-ally', where 'anaesthetic' is derived from Greek 'anaisthēsia' meaning 'lack of sensation'.

'anaesthetic' came from the Greek word 'anaisthēsia', which passed into modern English via Latin and French, and the adverbial form 'anaesthetically' was later formed in English.

Initially, it meant 'in a manner causing loss of sensation', and this meaning has remained consistent in modern usage.