What is the X in X-mas?
c.1300, from Old French deceite, fem. past participle of deceveir (see deceive).
Deceit is a shorter and more energetic word for deceitfulness, indicating the quality; it is also, but more rarely, used to express the act or manner of deceiving. The reverse is true of deception, which is properly the act or course by which one deceives, and not properly the quality; it may express the state of being deceived. Fraud is an act or series of acts of deceit by which one attempts to benefit himself at the expense of others. It is generally a breaking of the law; the others are not. [entry for "deceit" in "The Century Dictionary and Cyclopedia," 1902]