Seriously, though, a "muff" was a type of tubular, fur-lined, hand warmer that was worn attached to a belt so that it was positioned in front of you. (The closest things that we see these days are probably the hand warmers used in very cold weather by football players.) When you were keeping your hands warm, you were at a disadvantage to thieves because it would take a long time to remove your hands from the muff, reach for a gun, draw it, and fire it. Muff guns were derringer-sized, so they could be tucked inside the muff with your hands. If attacked, you already had one or two guns in hand. It made highwaymen think twice, back in the days when you didn't need permission to have a CCW. BTW - both men and women used muffs in the old days, but they came to be thought of more as a women's accessory in the 20th century.