'tumorless' originates from English, specifically the elements 'tumor' + suffix '-less', where 'tumor' ultimately comes from Latin 'tumor' (a swelling) and the suffix '-less' comes from Old English 'lēas' meaning 'without'.

'tumor' came from Latin 'tumor' (from the verb 'tumēre', to swell), entered Middle English as 'tumour', and in Modern English combined with the Old English-derived suffix '-less' to form the compound adjective 'tumorless'.

Initially, 'tumor' primarily meant 'a swelling'; over time it came to be used especially for neoplastic growths (tumors). 'Tumorless' therefore originally implied 'without swelling' and now specifically means 'without a tumor (neoplastic growth)'.