'eupneic' originates from Greek, specifically the elements 'eu-' and 'pnoē' (πνοή), where 'eu-' meant 'good/well' and 'pnoē' meant 'breath' or 'breathing'.

'eupneic' developed via New Latin/medical formation from Greek components (compare 'eupnea' from Greek 'eu-' + 'pnoē') and was taken into English as the adjective form meaning 'having eupnea'.

Initially, it meant 'good or normal breathing' in literal Greek-derived usage; over time it retained this specialized medical sense and now means 'having normal respiration'.