a feather in your cap

This article is about the English idiom. For the symbolism surrounding the giving of a white feather, see White feather.The term a feather in your cap is an English idiomatic phrase believed to have derived from the general custom in some cultures, of a warrior adding a new feather to their head-gear for every enemy slain, or in other cases from the custom of establishing the success of a hunter as being the first to bag a game bird by the plucking of the feathers of that prey and placing them in the hat band. The phrase today has altered to a more peaceful allusion, where it is used to refer to any laudable success or achievement by an individual that may help that person in the future.
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an honor, a credit to you, chalk one up for you Because you are Karen's teacher, her award is a feather in your cap.