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

'edema' entered English via Late Latin 'oedema' (from Greek) and via medical/Latin usage and eventually became the modern English 'edema' (also attested as 'oedema' in older British spelling).

Initially it meant 'a swelling'; over time it evolved into the medical term for 'localized or generalized swelling caused by excess fluid in tissues'.