They were called “the angry ones” because they would get very sad whenever they punished the evil people on earth. But some people realised that all they needed to do was call them “the nice ones,” and they would become calm again.
The furies are three sisters: Allecto (meaning endless), Tisiphone (meaning punishment), and Megaera (meaning rage). The three sisters looked like monsters. They would keep whips and cups of poison with them, so they could use it to hurt bad people.