Having defects or imperfections; not working correctly or containing errors.
From Old French 'faulte' meaning lack or failure, plus English suffix '-y'. From Latin 'fallere' meaning to deceive or fail. The sense of 'defective' developed from the notion of falling short or failing to meet standards.
The evolution from 'fault' as a geological crack to 'faulty' as defective reveals how we understand imperfection as a kind of break or fissure in expected performance. Interestingly, 'fault' in geology and 'fault' in blame share this concept of a fundamental break or failure.
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