Revelation 17:5

upon her foreheadwas a name written Probably not branded on the flesh, but tied on as a label, as Roman harlots actually did Wear their names.

Mystery Interpreters compare "the mystery of lawlessness" in 2 Thessalonians 2:7. The use of the word in Revelation 1:20 may illustrate its meaning here: it indicates that "Babylon the Great" is to be understood in a mystical sense.

of harlots Rather, of the harlots. She is the chief of these, and the cause of the rest being what they are. Therefore, though the fornications of Babylon are to be understood spiritually, yet her guilt includes the actual licentiousness of the Rome of Nero and Domitian, and in a wider sense "the sin of great cities" generally.