From Middle English tauni, tawne (“brownish-orange colour; cloth of this colour; sweet beverage of this colour”) [and other forms], from Anglo-Norman tawné, and Old French tané, tanné, tanney (“tan colour; cloth of this colour”), from tané (verb): see further at etymology 1. Sense 2.1 (“Eurasian bullfinch”) is due to the brown colour of the female.