'anaesthesiant' originates from French, specifically the word 'anesthésiant', where 'an-' meant 'without' and 'aisthēsis' meant 'sensation'.

'anesthésiant' was borrowed into English as 'anaesthesiant', and eventually became the modern English word 'anaesthesiant'.

Initially, it meant 'causing loss of sensation', and over time it evolved into its current meaning of 'a substance that induces anaesthesia'.