Aunt Sally
noun
Aunt Sal·ly -ˈsa-lē 
plural Aunt Sallies
British
: an object of criticism or contention
especially : one that is set up to invite criticism or be easily refuted
Word History
Etymology
Aunt Sally, name given to an effigy of a woman smoking a pipe set up as an amusement attraction at English fairs for patrons to throw missiles at
First Known Use
1859, in the meaning defined above