What is the X in X-mas?
1706, "stew pan," from French casserole "sauce pan" (16c.), diminutive of Middle French casse "pan" (14c.), from Provençal cassa "melting pan," from Medieval Latin cattia "pan, vessel," possibly from Greek kyathion, diminutive of kyathos "cup for the wine bowl." Originally the pan, since c.1930 also of the dishes cooked in it, via cookery phrases such as en casserole, à la casserole.