pumpernickel (n.)
"dark rye bread," 1756, pompernickel, from German (Westphalian dialect) Pumpernickel (1663), originally an abusive nickname for a stupid person, from pumpern "to break wind" + Nickel "goblin, lout, rascal," from proper name Niklaus (see Nicholas). An earlier German name for it was krankbrot, literally "sick-bread."