Meaning

noun an informal form of address for a man

noun a man who is much concerned with his dress and appearance

originUncertain, though likely a clipping of doodle (“fool, simpleton, mindless person”), perhaps with reference to the fashionable “Yankee Doodle dandy” in the 18th-century lyrics of the song “Yankee Doodle”; the word is first attested in 1883 as a New York City slang term of contempt for a “fastidious man, fop”. If so, then related to German Low German Dudeldop, Dudendop (“fool, dunce”), Saterland…

Etymology from Wiktionary, CC BY-SA 3.0