A Boston butt is the slightly wedged shaped portion of the pork shoulder above the standard picnic cut which includes the blade bone and the “lean butt” (which is boneless), both extensions of the tenderloin cut and can be used in place of the tenderloin. Generally the pork shoulder is considered a primal cut with the picnic and butt sections being sub-primal cuts however, some sources do refer to the butt as a primary cut.
Etymology and origins of the cut
In Colonial and Revolutionary New England butchers would use specialty barrels called butts to store a particular cut of pork. The butchering technique for this cut of pork also seems to have originated in New England and Boston, giving the cut the name “Boston butt”. A 1912 issue of the Agricultural Experiment Station of the University of Illinois bulletin states that the barrels were still in use for exports to Germany, Denmark and other European countries as well as for sale in the United States. However, the first known reference to the term does not appear in print until 1915 in the publication Hotel Monthly.