The word Armageddon appears only once in New Testament in Revelation 16:16. Is this a Greek word or a Hebrew word? What does this word mean?
1. First the word. "Armageddon" in English is translated from a NT Greek text that shows some variation at this point in the text. Of the edited versions of the GNT:
- Those that have "Har magedon" or "Harmagedon": W&H, UBS4/NA27, UBS5/NA28, NIV, Souter, Nestle 4, SBL, THGNT, Byzantine Text (=R&P), Apostolic Text = OC 1904, Jerome Vulgate
- Those that have "Armagedon": F35, TR, Clementine Vulgate.
- Those that have "Magedon": Majority Text (Possibly a mistake??)
Here I will assume that the "correct" text is "Harmagedon".
2. Meaning. The text of Rev 16:16 explicitly says that this word is Hebrew and thus must be read as "Har magedon" which is obviously, "Mountain of Megiddo". As any map or geography of Palestine shows, the town of Megiddo is on a plane but its closest mountain is mount Carmel.
3. Allusion. The key to understanding the book of Revelation and its symbols is to find the allusion each symbol makes to an OT story. Here, we are spoilt for choice as there were numerous battles fought at Meggido (Josh 12:21, 17:11, Judges 1:27, 1 Kings 4:12, 9:15, 2 Kings 9:27, 23:30, 1 Chron 7:29, 2 Chron 35:22, Zech 12:11). However, none of these involved the mountain of Megiddo, namely Carmel.
The most probable allusion is to the incident in 1 Kings 18 where Elijah and Ahab created the great contest of the Gods and the one who answered by fire was the true God. It was here that the people turned back to God and the prophets of Baal were defeated. This is a good parallel to the material under the sixth plague of Revelation.
4. Interpretation - That is the subject of another question.
I note that the Pulpit commentary reaches a similar conclusion:
By the employment of the Hebrew term, attention is called to the symbolical nature of the name. Similar cases occur in Revelation 9:11 and elsewhere in St. John's writings (see on Revelation 9:11). The correct reading, Αρμαγεδών, Har-Magedon, signifies "Mountain of Megiddo;" the Authorized Version, 'Αρμαγεδών, Armageddon, "City of Megiddo." Mount Megiddo possibly refers to Carmel, at the foot of which lay the Plain of Megiddo, which was well known to every Jew as a gathering place for hostile hosts and as the scene of many battles. It is referred to in Zechariah 12:11 as a type of woe, on account of the overthrow and death of Josiah having taken place there (2 Kings 23:29). Ahaziah also died there (2 Kings 9:27); and there also the Canaanitish kings were overthrown (Judges 5:19). The name is, therefore, indicative of battle and slaughter, and intimates the complete overthrow in store for the dragon and the kings of the earth, which is described later on (Revelation 19.).
The name "Armageddon" comes from the Greek word "Harmagedōn" (Ἁρμαγεδών) which is a transliteration of the Hebrew words "Har-Magedon" (הַר מְגִדּוֹן) meaning the hill of Megiddo, which overlooks a valley with a vast plane.
That valley is traditionally understood as the location of the final battle between the world's nations and God, when Jesus returns as King of Kings, to replace the kingdoms of this world with his own Kingdom of God.
But the battle itself won't be in the valley itself; Armageddon will simply be the staging area for what is to follow.
It is surprising that no one has suggested taking magedon as deriving from the secondary sense of the Hebrew gadad that means "to gather in troops or bands". The simple way in Hebrew to make a noun from a verb is to prefix a ma to the verbal form. Thus we have maged, "a place of gathering in troops", and the suffix o, meaning "his", yielding "his place of gathering troops". This is almost equivalent to the expressions in vss. 14, 16 — "to gather them (the kings and their armies) for the battle on the great day of God Almighty" — and would allude to the prophetic expectation of the gathering of the nations for judgment — The Expositor’s Bible Commentary p. 552