Filet mignon comes from the tenderloin, which has three parts (the butt, the center-cut, and the tail) and is shaped like a tapered tube. The butt is (unsurprisingly) the thicker end, and the tail is everything on the tapered end that is too small to turn into a full cut of beef. The rest is the center-cut, which is where filet mignon comes from. So you might have just heard the tail end referred to as the “tail,” the “filet tail,” or even the “tenderloin tail.” It’s usually cut up into small pieces for dishes that don’t require full cuts.