What is the X in X-mas?
early 15c., proccy, prokecye, "agency of one who acts instead of another; letter of power of attorney," contraction of Anglo-French procuracie (c.1300), from Medieval Latin procuratia "administration," from Latin procuratio "a caring for, management," from procurare "manage" (see procure). Also cf. proctor (n.). Meaning "person who acts in place of another" is from 1610s.