'edema' originates from Greek, specifically the word 'oidēma', where 'oid-' meant 'to swell'.

'edema' changed from Greek 'oidēma' into Latin/medical Neo-Latin 'œdema' (or 'oedema' in English spelling) and eventually became the modern English word 'edema'.

Initially, it meant 'a swelling', but over time it evolved into its current medical sense of 'an abnormal accumulation of fluid causing swelling'.