'ennoble' originates from Old French, specifically the word 'enoblir' / 'enoble', where the prefix 'en-' meant 'to make' and the root 'noble' (from Latin 'nobilis') meant 'well-known, of high birth or rank'.

'ennoble' changed from Old French 'enoblir'/'enoble' into Middle English as 'ennoblen' and eventually became the modern English verb 'ennoble'; the past participle form became 'ennobled'.

Initially, it meant 'to make someone of high birth or rank'; over time the sense broadened to include 'to elevate in dignity, honor, or moral quality', which is how it is commonly used now.