Meaning:
Its source is dux, a Latin name meaning "Leader."
Narrative:
This title of the minor nobility was used as a descriptive surname for those with a lordly manner. Its use as a diminutive form of the Gaelic-derived name Marmaduke was probably important to its status as a personal name.
American film star John Wayne (1907-1909) was known by this nickname. The enormous popularity of his tough-but-tender image has probably been the most important influence on the use of Duke in modern times, both as a formal name and as a casual nickname.