That's right, Steve! It was the Boston area where this practice of putting the "lesser cuts" in the wood butts was first practiced. Since that was the main sea port, most of these barrels were sold to ships. The shoulder cut with the blade bone, known as the "Boston butt," was unique to the Boston area butchers. The name became common, once the cut was shipped around the country. Still trying to find out why the name didn't stick in Boston! I bet it's more common now, though.
According to the National Pork Board, the "picnic shoulder" (sometimes called the picnic ham) is a little more vague. Best guesses say it's called that because the taste more resembles ham, when smoked, than the shoulder blade (Boston butt) cut does. It's believed that it was often substituted for the more expensive ham cut (from the hind leg) for informal meals, like outings and picnics.
Maybe we have a member from Boston that can answer the question about what they call them there!