As an adjective, describes a dull grayish-brown color; as a verb, means to make repeated requests for payment of a debt.
Color meaning from Old English 'dunn' meaning dark-colored. The debt-collection meaning comes from Joe Dun, a legendary 17th-century bailiff known for his persistence in collecting debts.
The connection between a drab brown color and pestering for money might seem random, but both meanings share the idea of something persistent and unavoidable. A dun-colored horse was considered reliable but unremarkable, much like a debt collector's steady persistence.
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