ministry (n.)

c. 1200, ministerie, "the office or function of a priest, a position in a church or monastery; service in matters of religion," from Old French menistere "service, ministry; position, post, employment" and directly from Latin ministerium "office, service, attendance, ministry," from minister "inferior, servant, priest's assistant" (see minister (n.)).

From late 14c. as "personal service or aid." From 1560s as "the body of ministers of religion, the clerical class." From 1710 as "the body of ministers of state in a country." It began to be used 1916 in the names of certain departments in the British government.