|A general synopsis of how Amen is a synretism of four gods: Nun, Ptah, Atum, and Ra, a god theory developed in Thebes (see: supreme god timeline), in the 12th dynasty Egypt, a general result of god reduction pressures. |
In the 18th dynasty (1549-1292BC), Amen was transformed into Amen-Ra and or Amen-Ra = Atum (see: supreme god timeline), as depicted below, depending; a "super-god" so to say, comprised of the powers of about ten or so of the main Egyptian gods of history, as shown adjacent (right), as representative of the various symbols: staffs (Set, Horus, Osiris), plums (Nun), sun disc (Ra), etc. This was the last point, in the evolution of gods, that it became near to silly to depict gods that were conceived or synretized after this point in time, per reason that it produced a visually characterize nonsense; Aten, e.g., one of the main post Amen-Ra gods, was simply depicted as the sun disc with hands. This is why most religions produced after this period tended to forbid the depiction of "god", as the result was childish or silly.
In c.1000BC, some of the superpower attributes of Amen, e.g. wings, was recast into the character of Zoroaster.
In 100AD, Plutarch, in his On Isis and Osiris, summarized Amen as follows: 
“Most people believe that Amoun is the name given to Zeus in the land of the Egyptians, a name which we, with slight alteration, pronounce Ammon. But Manetho of Sebennytus thinks that the meaning ‘concealed’ or ‘concealment’ likes in this world. Hectaecus of Abdera, however, says that the Egyptians use this expression one to another whenever they call to anyone, for the world is a form of address. When they, therefore, address the supreme god, whom they believe to be the same as the ‘universe’, as if he were invisible and concealed, and implore him to make himself visible and manifest to them, they use the word ‘Amoun’.”
Christianity | Prayer
In Christianity, the word "Amen" is said at the end of prayers, such as is touched on by Plutarch (100AD) above, a reverse of the name originally said to the beginning of prayers (e.g. Lord's prayer); most, however, are ignorant of the fact that this is an atrophied reference to the god Amen.
● Aron Nelson
1. (a) Budge, Wallis. (1904). The Gods of the Egyptians, Volume One (Amen-Ra, pg. 493). Dover, 1969.
(b) Budge, Wallis. (1904). The Gods of the Egyptians, Volume Two (Amen-Ra, pg. 7). Dover, 1969.
(c) Greenberg, Gary. (2000). 101 Myths of the Bible: How Ancient Scribes Invented Biblical History (roots, pgs. 3-4; pgs. 4-5). Source Books.
2. Thims, Libb. (2016). Smart Atheism: For Kids (pdf | 309-pgs) (Amen, pg. 115). Publisher.
3. Plutarch. (c.100AD). Isis and Osiris; in: Plutarch's Moralia, Volume Five (pg. 25) (Introduction: Victor Hanson). Harvard University Press.
● Jordan, Michael. (1993). Encyclopedia of Gods: Over 2,500 Deities of the World (Amun, pg. 15). Facts on File, Inc.
● Amun – Wikipedia.