What is the X in X-mas?
late 14c., "function of a priest," from Old French menistere "service, ministry; position, post, employment," and directly from Latin ministerium "office, service, attendance, ministry," from minister (see minister (n.)). Began to be used 1916 as name of certain departments in British government.
in Christianity, the office held by persons who are set apart by ecclesiastical authority to be ministers in the church or whose call to special vocational service in a church is afforded some measure of general recognition. The type of ministry varies in the different churches. That which developed in the early church and is retained by the Roman Catholic, Eastern Orthodox, Old Catholic, Anglican, and some Protestant churches is episcopal (see episcopacy) and is based on the three orders, or offices, of bishop, priest, and deacon.