small dark spots on skin, small burrowing mammals with tiny eyes, or agents working undercover for a government agency.
From Old English 'mol' (dark spot) for skin marks; from different Germanic roots for the animal; from French 'taupe' (mole the animal) by metaphorical extension to spies.
The word 'mole' in espionage comes from the animal's habit of burrowing underground—spies hide in plain sight, just like moles hide underground, making it the perfect metaphor that influenced Cold War terminology!
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