'apnoea' originates from Greek, specifically the word 'apnoia', where 'a-' meant 'without' and 'pnoē' meant 'breath'.

'apnoea' passed into Late Latin/medical Latin as 'apnoea' (from Greek 'apnoia') and was then adopted into English as 'apnoea'; the alternate American spelling 'apnea' is a later orthographic variant.

Initially it literally meant 'without breath', but over time it evolved into the medical sense of a temporary cessation of breathing (now especially used for sleep-related breathing pauses).