A sham is a fake. If you frequently order products advertised on late-night, hour-long television commercials, you’ve probably ended up with at least one item that was a sham. All-purpose, industrial strength stain remover, anyone?
Sham can be used to refer to people as well as to things. Remember that doctor from the late-night TV commercial advertising UltraMiracleCure vitamin pills? He’s probably a sham, or a quack. Some sources claim that the word sham originated in the 17th century and was derived from the English word shame, but who knows? Maybe that theory’s a sham too.