Minecraft wiki entry for Sham, associated text: There was a feature in Minecraft Beta 1.3 through Beta 1.9 Prerelease 5 where a zombie or a skeleton had the chance of spawning when a player slept. This is similar to the sham's behavior except the bed itself is the monster.
The sham was based on a minifigure made by Matel which in turn was based on a skin with the same name in the "Campfire Tales" skin pack.
The sham skin in the "Campfire Tales" skin pack was renamed to the bedlam. This was after it appeared in the episode and isn't referred to as such in the Minecraft Mini-Series.
The word "sham" is used to mean something that is false or pretending to be something it's not. A "pillow sham" is a decorative pillowcase for storing pillows when they aren't being used.
The word "Bedlam" is used to convey a setting or scene of mayhem or confusion.