Vote for this answer. Here's one possibility: I heard from Gary himself that before they were famous, they would play in the Fiddle and Steele Guitar Club in Nashville, TN. They didn't have a name at the time and so they told the audience that if they have any ideas, to see them after the show. Well, after the show, a guy came up to them and said that he had a band in high school and they were called Rascal Flatts. He said they could use that name if they wanted to.