Invocations of God or holiness -- sometimes even in idle profane language -- damages devils, demons, and other unholy beings, with anything from mild pain to serious injury -- or maybe they just don't like it. They may be unable to utter the names and so have to resort to euphemisms. It tends to be a much weaker reaction than It Burns!, for the obvious reason that it's a lot easier to invoke the names than to lug about a holy object. To prevent its being too much of a Weaksauce Weakness, idle invocation may not cut it, and the character may have to be holy, at least to do serious damage. Where Good Hurts Evil meets up with Words Can Break My Bones and I Know Your True Name, and they decide to form a Power Trio.
- In Isaac Asimov's "Pact", the devil talks about er -- Above.
- Lord of the Rings: "...all blades perish that pierce that dreadful King. More deadly to him was the name of Elbereth".
- Sam and Frodo drive The Watchers in Cirith Ungol through this.
- In Poul Anderson's Three Hearts and Three Lions, the witch warns Holger not to pray or cross himself. He's a Na´ve Newcomer and doesn't realize this means she's summoning a demon.
- In The Armor of Light, Marlowe repeals a demon by invoking a holy name, and thinks he has conclusively shown that it is the name itself and not the virtue or holiness of the man speaking it that is effacious.
- In the book version of Darby O'Gill and the Little People the Little People wince at anything pious. True to folklore much of which thinks of the Fey as spirits under a divine curse for some sin in the past, usually not taking sides against Satan.
- Supernatural: Demons flinch at the sound of God's name, though only if it's said in Latin as Christo.
- Dungeons & Dragons has the cleric spell Holy Word as well as the evil equivalent Blasphemy. They're not that discriminatory when it comes to hurting beings, but they do their worst stuff to diametrically opposed beings (evil for Holy World, good for Blasphemy).
- Nethack: most monsters are repelled by engraving Elbereth, and cannot attack a character who is praying if the prayer will succeed.
- In RetroMUD there is a God of Good named Sikkar. Good aligned spiritual spell-casters can learn a spell called 'Holy Word', which works by invoking the true name of Sikkar and harms evil beings. Inverted with the evil equivalent 'blaspheme', which works by invoking the true name of Sikkar backwards and harms good beings.
- In Cosmic Christmas, Gabriel encounters a demon who claims to be defecting back to the angels. Unsure whether to trust him, Gabriel asks him to sing a hymn with him. The demon only sputter, and claims to have forgotten the words, before the music from the hymn drives him off.
Hello, Unknown Troper. You'll need to get known to lend a hand here.