From leitourgos; to be a public servant, i.e. (by analogy) to perform religious or charitable functions (worship, obey, relieve) -- minister.
see GREEK leitourgos
1. in Attic, especially the orators, "to serve the state at one's own cost; to assume an office which must be administered at one's own expense; to discharge a public office at one's own cost; to render public service to the state" (cf. Melanchthon in Apology, Confessions, Augustine, p. 270f (Corpus Reformat. edition Bindseil (post Bretschn.) vol. xxvli., p. 623, and F. Francke, Conf. Luth., Part i., p. 271 note (Lipsius 1846)); Wolf, Demosthenes, Lept., p. 85ff; Böckh, Athen. Staatshaush. i., p. 480ff; Lübker, Reallex. des class. Alterth. (or Smith, Dict. of Greek and Rom. Antiq.) under the word λειτουργία).
2. universally, to do service, to perform a work; Vulg.ministro (A. V. to minister);
a. of the priests and Levites who were busied with the sacred rites in the tabernacle or the temple (so the Sept. often for שֵׁרֵת; as Numbers 18:2; Exodus 28:31, 39; Exodus 29:30; Joel 1:9, etc.; several times for עָבַד, Numbers 4:37, 39; Numbers 16:9; Numbers 18:6f; add, Sir. 4:14 (