It's a fictional character - a Dutch historian living in New York - invented by Washington Irving as the supposed author of "Rip van Winkle" and various other Irving works. See Wikipedia:
Do you mean "The Legend of Sleepy Hollow?" Washington Irving's classic short story is a part of his "The Sketchbook of Geoffrey Crayon" with Geoffrey Crayon being his pen name under which he wrote the book. However, the narrator of the story is never given. As Crayon, Irving claims the story was "Found amoung the papers of the late Diedrich Knickerbocker." In the postscript, writing as Knickerbocker (the postscript is signed D.K. and at the very start of the postscript is a message saying "Found in the handwriting of Mr. Knickerbocker"), Irving describes the narrator as "a pleasant, shabby, gentlemanly old fellow, in pepper and salt clothes, with a sadly humourous face." This is Knickerbocker telling the reader about the narrator of the story, making it clear it's not Knickerbocker himself. Crayon makes it clear he's adding something written by Knickerbocker who is supposed to now be dead. Ultimately, as both are in reality Washington Irving, it's he who is doing the writing, and using a nameless character as the narrator of the story.
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It's a fictional character - a Dutch historian living in New York - invented by Washington Irving as the supposed author of "Rip van Winkle" and various other Irving works. See Wikipedia:
Diedrich Knickerbocker
Do you mean "The Legend of Sleepy Hollow?" Washington Irving's classic short story is a part of his "The Sketchbook of Geoffrey Crayon" with Geoffrey Crayon being his pen name under which he wrote the book. However, the narrator of the story is never given. As Crayon, Irving claims the story was "Found amoung the papers of the late Diedrich Knickerbocker." In the postscript, writing as Knickerbocker (the postscript is signed D.K. and at the very start of the postscript is a message saying "Found in the handwriting of Mr. Knickerbocker"), Irving describes the narrator as "a pleasant, shabby, gentlemanly old fellow, in pepper and salt clothes, with a sadly humourous face." This is Knickerbocker telling the reader about the narrator of the story, making it clear it's not Knickerbocker himself. Crayon makes it clear he's adding something written by Knickerbocker who is supposed to now be dead. Ultimately, as both are in reality Washington Irving, it's he who is doing the writing, and using a nameless character as the narrator of the story.