I don't understand the term. Would black people say that when a black person is tried with an all white or mostly white jury that it would be called a jury of your peers? What about if you are a staunch Republican (we'll just call him Donald J Trump) and you have a trial in a deep blue city inside a deep blue state (with a deep blue DA and deep blue prosecutors and a deep blue judge)? Would that be called a jury of your peers? What in the hell is a peer?
Why they are people who check all the same boxes as you. So, for instance, if you are a serial killer, your peers would be 12 other serial killers who get to decide if you are worthy of being in their Members Only club.