The most free from dirt, germs, or impurities; or most morally pure.
From Old English 'clæne,' related to 'clay' and originally meant 'free from dirt or stickiness.' The meaning expanded to include moral purity by the Middle Ages.
The superlative form 'cleanest' reminds us that humans have always valued cleanliness—archaeologists find ancient bathing systems in civilizations thousands of years old!
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