'cancer-free' is a modern English compound formed from 'cancer' and 'free'. 'cancer' originates from Latin, specifically the word 'cancer' (from Greek 'karkinos'), where 'cancer' originally meant 'crab'. 'free' originates from Old English, specifically the word 'freo', where 'freo' meant 'not in bondage or exempt'.

'cancer' changed from Greek 'karkinos' to Latin 'cancer' and entered English as 'cancer' in Middle English; 'free' changed from Old English 'freo' (from Proto-Germanic *frijaz) and evolved into the modern English word 'free'. The compound 'cancer-free' is a descriptive compound formed in modern English to mean 'without cancer'.

Initially, 'cancer' referred metaphorically to a 'crab' (because of the shape/appearance) and later came to denote the disease; 'free' initially meant 'not in bondage' and broadened to mean 'without' or 'not affected by'. Together they now mean 'without cancer'.