From a Washington Irving character, it's a nickname for a New Yorker, Dutch-descended or otherwise
[DOC] [TLE] Texts for Craig White's Literature Courses UHCL - uhcl.edu [PAR] Washington Irving ... [one of Irving's several pseudonyms or pen names, meant to 
suggest a New Yorker of earlier Dutch generations] ... character of its inhabitants, 
who are descendants from the original Dutch settlers [of New ...... the flogger of 
urchins [<Ichabod] be otherwise than animated and joyous?