Duncan is the English form of the Scottish Gaelic Donnchadh, from donn, "brown", and cath, "battle", usually rendered as "brown warrior" or dark-haired warrior. Two medieval kings of Scotland bore it, the first of them immortalized as the murdered King Duncan in Shakespeare's Macbeth. Duncan ranked number 447 in the United States in 2000, its best year in this century, and has slipped out of the top 1000 since 2019, standing at number 1124 in 2025.