Merriam-Webster Collegiate Dictionary - duplicity

 noun  (plural -ties)  Etymology: Middle English duplicite, from Middle French, from Late Latin duplicitat-, duplicitas, from Latin duplex  Date: 15th century  1. contradictory doubleness of thought, speech, or action; especially the belying of one's true intentions by deceptive words or action  2. the quality or state of being double or twofold  3. the technically incorrect use of two or more distinct items (as claims, charges, or defenses) in a single legal action