Webster's 1828 Dictionary's Definition of "Impostor" includes "a deceiver under a false character."
Noah Webster, 1828 Webster's Dictionary, (The Editorium, 1828), "Impostor," accessed November 8, 2022
IMPOS'TOR, noun [Low Latin impostor from impono. See Impose.]
One who imposes on others; a person who assumes a character for the purpose of deception; a deceiver under a false character. It seems to be yet unsettled, whether Perkin Warbeck was an impostor A religious impostor may be one who assumes the character of a preacher, without authority; or one who falsely pretends to an extraordinary commission from heaven, and terrifies people with denunciations of judgments.