'defect-free' is a compound of the noun 'defect' and the adjective 'free'. 'defect' originates from Latin, specifically the word 'defectus' (from the verb 'deficere'), where 'de-' meant 'away' or 'off' and 'ficere'/'ficere' (related to 'facere') conveyed the idea of 'to do' or 'to make'. 'free' originates from Old English 'frēo', meaning 'not in bondage; exempt'.

'defect' passed into English via Old French/Latin influence (Latin 'defectus' → Old French/Medieval Latin forms → Middle English 'defect'). 'free' descended from Old English 'frēo' through Middle English to modern 'free'. The compound 'defect-free' is a Modern English formation combining these elements to describe something lacking defects.

Initially, 'defect' carried the sense of 'failure' or 'a falling away' and 'free' meant 'not bound'; combined, the phrase originally meant 'not having failures or faults' and has retained that core meaning to describe items or systems without defects.