I found that title while researching someone's ancestors. They had two who had that title. According to what I read, the groom wasn't really there to wipe the royal butt. He was there to look at the crap and make sure the king was healthy. And he might possibly have cleaned the stool. It was a prestigious position, as he would be around the king more than anyone else and knew everything that was going on. The "stool" was a box with a padded top with a hole in it. There was a door on the side for removing the used chamber pot to empty it. They were typically covered in purple velvet cloth tacked down with gold tacks. There was also a hinged lid to hold in the odor.