feather in one's cap

Example: “Winning the national award was a real feather in her cap.”

Origin: The custom of marking a personal achievement with a feather worn visibly in one's headwear shows up independently across several unrelated cultures, suggesting the same idea occurred to different peoples on its own rather than spreading from a single source. English writer Richard Hansard documented one striking version in 1599: among Hungarians of the day, only a man who had killed a Turk in battle was permitted to wear a feather, with the number of feathers in his cap openly announcing his tally of slain enemies. Many Native American traditions similarly awarded a feather for a warrior's brave deed, and feathered headwear as a mark of distinction goes back to antiquity across much of Europe as well. The English figurative phrase — an achievement worth being proud of, whether or not any actual feather is involved — is documented in Britain by 1734.