'azygous' originates from New Latin, specifically from Greek-derived 'azygo-' (from Greek 'azygoûs'), where 'a-' meant 'not' and 'zygos' meant 'yoked, paired'.

'azygous' changed from Greek 'azygoûs' (ἀζυγός) into New Latin forms such as 'azygo-' and was later adopted into modern English as 'azygous'.

Initially it meant 'not yoked/paired', and over time it has come to mean 'unpaired; occurring singly', especially in anatomical contexts.