'oedemata' originates from Greek, specifically the word 'oidēma' (οἴδημα), where the root 'oid-' meant 'to swell'.

'oedemata' passed into Latin and Medieval Latin as 'oedema' (plural 'oedemata'), and later entered English as 'oedema' with the Greek plural 'oedemata' sometimes used in medical contexts.

Initially it meant 'a swelling', and over time it retained that sense but became more specifically used for 'swelling due to abnormal fluid accumulation' in medical usage.