'apnoeal' originates from modern medical English formation based on 'apnoea', which ultimately comes from Greek 'apnoia' where the prefix 'a-' meant 'without' and 'pnoē' (πνοή) meant 'breath'.

'apnoeal' was formed in English by adding the adjective-forming suffix '-al' to 'apnoea'. 'Apnoea' itself was borrowed into English from modern Latin/medical Latin 'apnoea', which in turn was derived from Greek 'apnoia' (ἀπνοία).

Initially derived from the Greek sense 'without breath', it evolved into the clinical sense 'a temporary cessation of breathing' and the adjective 'apnoeal' now means 'relating to or showing such cessations'.