'apostume' originates from Latin, specifically the word 'apostema', which in turn comes from Greek 'apóstēma', where 'apo-' meant 'away' and the element related to 'stēma' (from the verb 'histēmi') conveyed the sense of 'that which stands (apart)' (used for a swelling or separated collection).

'apostume' changed from the Medieval Latin word 'apostema' and was borrowed into Middle English (as 'apostume' or similar spellings); it retained the same basic form into early modern English but later fell out of common use, being replaced by the more common word 'abscess'.

Initially it meant 'a swelling or collection (standing apart)', specifically an abscess; over time the core medical meaning remained but the word became archaic and was largely replaced by 'abscess' in modern usage.