Covered or stained with small scattered marks or spots of dirt or dark material.
From the prefix 'be-' (meaning to cover or affect) combined with 'smottered,' which may derive from Middle English 'smotter' meaning to stain or spot. The term evolved to describe anything speckled or marred with scattered blemishes.
This wonderfully specific word captures what happens when you've tried to clean something but only partially succeeded—it's the visual equivalent of a half-hearted effort, which is why it appears so often in Victorian literature describing people who've been caught in a rainstorm.
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