Swear Toads are mentioned a few times throughout in the series, a minor running gag. What makes them different from normal toads is that fact that they spontaneously shout profanity, presumably in Gnommish. They are also mildly venomous. According to The Artemis Fowl Files, Holly Short was once bitten in the behind by a swear toad, causing much swelling. She quotes that she hopes Artemis Fowl will never find out about that.