Step 1 : Introduction to the question "3. The word Armageddon only appears in one book of the Protestant Bible; which apocalyptic book is it?"
...1. Revelation 2. Daniel 3. Isaiah 4. I Thessalonians Armageddon only appears in Rev. 16:16. The word comes from the Hebrew har meggido, which means Mount Megiddo or Mountain of Megiddo. Considering there are no mountains in the vicinity of the Old Testament(OT) city of Megiddo, mentioned ten times in the OT, but only a plain, many scholars have concluded that the language is symbolic rather than literal. Whether the New Testament language is to be taken literally of symbolically, the Battle of Armageddon has come to be known as the ultimate battle between good and evil that will usher in a new age. This common theme is found not only in traditional Christianity but also in Jehovah's Witnesses teachings, in Seventh Day Adventist teachings, in Islam, and in the Bah�'� faith. Although the books of Isaiah and Daniel are prophetic in nature, they are not considered apocalyptic. I Thessalonians also has some passages that speak about the ends times but it is not considered apocalyptic either.