As my butcher would say “the butt has nothing to do with the ass”. The butt actually comes from the upper shoulder of the front leg of the pig and is the most common cut used for pulled pork and carnitas. In pre war America, these less valued cuts were often packed into barrels that were known as butts with the butchers in Boston developing the cut. Hence the name.
A.K.A Pork Shoulder, Blade Roast. The lower part of the shoulder is know as the picnic shoulder or picnic ham.
Be sure to season the meat liberally with a dry rub. Low and slow (225º for 5-8 hours) produces tender and moist pulled pork. Or, you can indirectly grill the pork shoulder for 2-3 hours at 325º. Let rest for 20-30 minutes before serving.