The term dates back at least to the 1870s in the United States, close to the peak of Irish migration. The OED's recent revisions link Patsy with Pat and Paddy, the stereotype of the bogtrotter just off the boat. The American Heritage Dictionary and Online Etymology Dictionary quotes the OED it may derive from the Italian pazzo (“madman”), and south Italian dialect paccio (“fool”). Another possibility is the term derives from Patsy Bolivar, a character in an 1880s minstrel skit who was blamed whenever anything went wrong, in Broadway musical comedies, for example in The Errand Boy  and Patsy in Politics .
patsy (plural patsies)
- (informal, derogatory) A person who is taken advantage of, especially by being cheated or blamed for something.
- (by being cheated): sucker; see also Thesaurus:dupe
- (by being blamed): scapegoat; see also Thesaurus:scapegoat