'tumor-promoting' is a modern English compound formed from 'tumor' + 'promoting'. 'tumor' originates from Latin, specifically the word 'tumor' (meaning 'a swelling'), while 'promoting' comes from Latin 'promovere', where the prefix 'pro-' meant 'forward' and 'movere' meant 'to move'.

'tumor' entered English via Medieval Latin 'tumor' and Old French 'tumeur'; 'promote' entered English from Latin 'promovere' through Old French (e.g. 'promouvoir') into Middle English (e.g. 'promoten'), and the compound 'tumor-promoting' arose in modern biomedical English to describe agents or effects that encourage tumor growth.

Initially 'tumor' denoted 'a swelling' and 'promote' meant 'to move forward or advance'; over time, with advances in medical science, the combined form 'tumor-promoting' evolved to mean specifically 'encouraging tumor growth or progression' in biological and clinical contexts.