Completely clean with no spots, marks, or dirt; also meaning absolutely perfect or having no flaws.
From 'spot' (a mark or blemish) plus '-less' suffix. The word has been used in English since the 1600s for both literal cleanliness and metaphorical purity.
We use 'spotless' to mean morally perfect too (a 'spotless reputation')—it's a perfect example of how physical cleanliness became metaphorically linked to moral purity across nearly all cultures, probably because dirt is universally visible and easy to understand.
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