This familiar word is an adjective, meaning, “true,” or “faithful.” In Rev. 3:14 Christ is called, “the Amen, the true and faithful witness.” ...
The word was well known to the Hebrews. In the trial by ordeal, common among the ancients, the accused person was made to drink a potion cursed by the officiating priest before the altar of Jehovah. An oath was then read, and the suspect responded, “Amen, Amen!” (So be it!). (Deut. 27:14-26, the Levites were commanded to put a motion before the assembly of Israel, that twelve offenses, specified, be declared grave crimes, some of them calling for the penalty of death, and that the motion was to be accepted by the people answering, “Amen.”
In Isaiah 65:16 the Lord is called the “God of Truth,” which is a translation of the original, “God of Amen.”
Our Lord often repeated the word for the sake of emphasis: “Amen, amen, I say unto you.” (14:12, etc.) The translators have, “Verily, verily, I say unto you.”
Some of the Psalms, for example 41 and 72, end with, “Amen and Amen!” and the Christian churches very early adopted this form, as we infer from 1 Cor. 14:16, where St. Paul asks: “If thou shalt bless with the spirit”—and not with the understanding—“how shall the unlearned say Amen an thy giving thanks, seeing he understandeth not what thou sayest?” Justin Martyr (100-165) informs us that, at the Sacrament meetings, the entire congregation responded to the benediction by saying, Amen!
But Amen was also the Egyptian god of whom Dr. Wallis Budge (Osiris and the Resurrection, Vol. 1, p. 360) says that he was a god unlike any of the other gods of Egypt, for he symbolized the hidden Power, the source of the world and all life, the highest conception of the Deity which the Egyptians ever imagined.
The famous Egyptian pharaoh, Rameses II, generally supposed to have been the pharaoh of the oppression of the Israelites, is said to have offered up this prayer to Ammon, after having been defeated in a battle:
“I call upon thee, my Father Ammon! My many soldiers have abandoned me; none of my horsemen hath looked towards me; and when I called them, none hath listened to my voice. But I believe that Ammon is worth more to me than a million of soldiers, than a hundred thousand horsemen.” (Hibbert Lectures, 1879, p. 228.)