Thimblerig

Thimblerig \THIM-buhl-rig\ , verb;
1. To cheat of swindle, as in the traditional shell game known as thimblerig
noun;
1. A game in which the operator rapidly moves about three inverted thimbles, often with sleight of hand, one of which conceals a token, the other player betting on which thimble the token is under

Thimblerig dates to the 1825 and is a combination of thimble + rig where rig means "a fraudulent auction; a mock auction". Thimble goes back to Old English þymel  ("sheath or covering for the thumb") which is a combination of thuma + -el where thuma is the forebear of thumb and -el is a suffix used in forming names of instruments. The addition of the -b- happened in the mid-15th century and it is excrescent, which means it was added without etymological justification. In all likelihood it was added because there is a faint [b] sound produced when [m] is immediately followed by [l].

Today's word and the first definition were both taken from Dictionary.com's 'Word of the Day' for Monday, January 31
Etymologies come from the Oxford English Dictionary and/or Etymonline.com