Boston butt or pork butt is the American name for a cut of pork that comes from the upper part of the shoulder from the front leg and may contain the blade bone. Boston butt is the most common cut used for pulled pork, a staple of barbecue in the southern United States.
In the United Kingdom, Boston butt is known as pork shoulder on the bone, since regular pork shoulder normally has the bone removed and then rolled and tied back into a joint.
In pre-revolutionary New England and into the American Revolutionary War, New England butchers tended to take less prized cuts of pork like hams and shoulders and pack them into barrels for storage and transport, known as a butt. This particular shoulder cut became known around the country as a Boston specialty, and hence it became the "Boston butt". In the UK it is known as "pork hand and spring", or simply "pork hand", or, as noted above, "pork shoulder on the bone".
In Mexican Spanish, this cut is also known as the espaldilla (literally "little back").
In Argentina, this cut is incredibly popular and is known as bondiola.
In Korea, the cut is known as moksal (목살; literally "neck meat").