From a Washington Irving character, it's a nickname for a New Yorker, Dutch-descended or otherwise
[DOC] [TLE] New Netherland - Wikipedia [PAR] New Netherland was a 17th-century colonial province of the Seven United 
Netherlands that ... During its first decades, New Netherland was settled rather 
slowly, partially as .... Dutch trading companies in the newly charted areas (
especially in New York ..... Irving's romantic vision of an enlightened, languid 
Dutch yeomanry... [DOC] [TLE] Origins of The Name - KNICKERBOCKER [PAR] A name now most famous throughout New York and the United States.