'chemotherapeutic' originates from Modern English as a compound of the combining form 'chemo-' and the adjective 'therapeutic'. 'Chemo-' ultimately derives from Greek 'khēmía' (or Latinized forms) where 'khēmía' meant 'alchemy' or 'chemistry', and 'therapeutic' comes from Greek 'therapeuein' where 'therapeuein' meant 'to serve, attend, or heal'.

'chemotherapeutic' developed via New/Modern English from earlier formations such as Neo-Latin/Modern scientific coinages (e.g. 'chemotherapy' + adjectival suffix '-tic'); 'chemotherapy' itself was coined in the 20th century from 'chemo-' + 'therapy' (from Greek via Latin/French 'therapeutique'), and the adjective form followed to yield 'chemotherapeutic'.

Initially the parts meant 'chemical' (chemo-) and 'pertaining to treatment' (therapeutic); over time the combined term has come to specifically denote treatment using chemical agents (especially drugs used to treat cancer), a meaning that has remained consistent in modern medical usage.