According to egullet.com, bread and butter pickles are named such because during the Depression, they were as regular a part of a diet as bread and butter. The difference between bread and butter pickles and sweet pickles is just a few ingredients. Sweet pickles use cinnamon, cloves, and allspice in a vinegar-sugar brine. Bread and butter pickles are made with turmeric. mustard, and onion in a vinegar-sugar brine.

Don't know if this is the "real scoop" though, DaveO