50 But now we shall speak of what is before us. For such measures will he, too, devise, seeking to afflict the saints in every way. For the prophet and apostle says: “Here is wisdom, Let him that has understanding count the number of the beast; for it is the number of a man, and his number is six hundred threescore and six.” With respect to his name, it is not in our power to explain it exactly, as the blessed John understood it and was instructed about it, but only to give a conjectural account of it; for when he appears, the blessed one will show us what we seek to know.
Yet as far as our doubtful apprehension of the matter goes, we may speak. Many names indeed we find, the letters of which are the equivalent of this number: such as, for instance, the word Titan, an ancient and notable name; or Evanthas, for it too makes up the same number; and many others which might be found. But, as we have already said, the wound of the first beast was healed, and he (the second beast) was to make the image speak, that is to say, he should be powerful; and it is manifest to all that those who at present still hold the power are Latins.
If, then, we take the name as the name of a single man, it becomes Latinus. Wherefore we ought neither to give it out as if this were certainly his name, nor again ignore the fact that he may not be otherwise designated. But having the mystery of God in our heart, we ought in fear to keep faithfully what has been told us by the blessed prophets, in order that when those things come to pass, we may be prepared for them, and not deceived. For when the times advance, he too, of whom these thing are said, will be manifested.
Source: The Antichrist (New Advent)