I've herad Briant, Bryant also..
My father spoke with my Great Uncle, Earnest Brians. He had a quite extensive collection of geneology records (they seem to have been lost since he passed on). The name change was apparently because someone, one of the Brians' killed someone and might have moved and changed his name as a result. Not certain on the time frame, but think late 1700s because of the name change, tracking/research issues I'm running into.