No more that thane of Cawdor shall deceive
Our bosom interest: go pronounce his present death,
And with his former title greet Macbeth.

– William Shakespeare

Macbeth, Act 1, Scene 2. King Duncan decrees that Macbeth be honored as the new Thane of Cawdor, the title being vacant due to the treason of the previous thane. It is ironic that Duncan says the Thane of Cawdor will no longer deceive, because that is exactly what Macbeth does by killing the King.