What is the X in X-mas?
1680s, from French dupe "deceived person," from Middle French duppe (early 15c.), thieves' jargon, perhaps from phrase de huppe "of the hoopoe," an extravagantly crested and reputedly stupid bird.
1704, from dupe (n.). Related: Duped; duping.
A duplicate copy of a film or text (1902+)