'non-oedematous' originates from Greek and Latin elements: the Greek word 'oidēma' (οἴδημα) meaning 'swelling' (entered English as 'oedema') combined with the prefix 'non-' (from Latin 'non') meaning 'not'.

The Greek 'oidēma' passed into Latin and then into English as 'oedema'; in some varieties (especially American English) the spelling was simplified to 'edema'. The adjective form 'oedematous'/ 'edematous' developed from that root, and the negative prefix 'non-' was applied to form 'non-oedematous'.

Initially the root meant 'swelling'; over time it came to denote the medical condition 'oedema' and adjectival forms meant 'characterized by swelling'. 'Non-oedematous' now specifically means 'not showing swelling (no oedema)'.