feather in one's cap

Etymology:

• The placing of a feather in a hat has been a symbol of achievement that has arisen in several cultures, apparently independently. The English writer and traveller Richard Hansard recorded it in his Description of Hungary, 1599:
• "It hath been an antient custom among them that none should wear a fether but he who had killed a Turk, to whom onlie yt was lawful to shew the number of his slaine enemys by the number of fethers in his cappe."
• The Native American tradition of adding a feather to the head-dress of any warrior who performed a brave act is well known.