From the article: The Pope of Rome is the Antichrist
Question: Who is the antichrist?
Answer: With all Protestants we reply: The pope of Rome. The papists deny this strongly.
We shall first confirm our opinion, and then answer the objections of the papists. In order to perceive the force of our argumentation all the more clearly, one must view all our arguments comprehensively, that is, as one argument. Our proof will consist of several parts, each of which, when considered independently, is convincing in and of itself.
Our first proof is derived from the name itself, which means darkness. “Here is wisdom. Let him that hath understanding count the number of the beast: for it is the number of a man; and his number is six hundred threescore and six” (Rev 13:18). In chapter 15:2 this is referred to as the number of his name. The Lord did not want to call him expressly by name; possibly that he be not hindered in his pursuit, or because the Lord did not wish to reveal His mysteries to everyone (cf. Matt 13:13). It is irrefutable that the reference here is to the antichrist. How to prove this, however, is not equally clear to everyone. To identify him here as such, one must note: 1) John wrote in the Greek language, and the Greek language uses its letters also as numbers; 2) the letters of this number would convey the name of a man. We also read of “… the mark of his name” (Rev 14:11); “… the number of his name” (Rev 15:2); 3) his name would be written with such letters which together would constitute the number six hundred sixty-six.
First of all, Irenaeus, a disciple of Polycarp who himself was a disciple of John, arrived at the spelling of lateino” (lateinos), and concluded thereby that the antichrist would come forth from Italy and from the Latin church. Italy, or at least a portion of it, had a king prior to the birth of Christ. His name was Latinus, who was a son of Faunus, the son of Picus, the son of Saturnus, the son of Janus, the first king of Italy. Italy, or that portion of Italy which surrounds Rome, is called Latinum after this Latinus, and the language spoken there was called Latin, which is true until this very day. Latinus is written in Greek as Lateinos and these letters irrefutably represent the number 666. Therefore, in pursuit of the antichrist one is as it were led by the hand to Rome, to the Latin church and to her bishop, who later was called papa or pope, that is, father. The pope was the proprietor of Latinum, where Latinus was king before Rome was built. He established himself in the Latin Church, for the Western church was long known by the name of Latin Church. Whenever a general ecclesiastical gathering convened, the Western bishops were referred to as Latin bishops, and the Eastern bishops as Greek bishops. Until this very day the pope still uses the Latin language in his directives and decrees. Throughout the entire world the church service, the mass, etc, are conducted in the Latin language, which must be viewed as an extraordinary providence of God, whereby it is clearly proven that he is the antichrist…
Read article here.