It depends which country you are talking about.
A white feather has been a traditional symbol of cowardice within the British Army and throughout the British Empire. It was given to someone as a sign that the giver considers them a coward. It came from cockfighting, and the belief that a cockerel sporting a white feather in its tail is likely to be a poor fighter.
However, in the USA, a white feather indicates extraordinary bravery and excellence in combat marksmanship!
There's a famous book, The Four Feathers (by a British author so it's about someone accused of cowardice!) which has been made into a damn good movie.