Man of Sin
(The). (2 Thess. ii. 3). The Roman Catholics say the Man of Sin is Antichrist. The Puritans applied the term to the Pope of Rome; the Fifth-Monarchy men to Cromwell; many modern theologians apply it to that “wicked one” (identical with the “last horn” of Dan. vii.) who is to immediately precede the second advent.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894