Why are evil angels called “devils,” or slanderers and deceivers?

They are so called because they continually set snares to deceive humans and provoke in them evil desires. As the Lord Christ said to the unbelieving Jews: “You are of your father the devil, and the desires of your father, you want to do. He was a murderer from the beginning, and does not stand in the truth, because there is no truth in him. When he speaks a lie, he speaks from his own resources, for he is a liar and the father of it” (John 8:44).