This is the "real" traditional Pennsylvania Dutch "pot pie" that I've been eating since I was a kid here in Lancaster County, Pa. Mom, and Grandma didn't use a slow cooker, but stewed chicken with celery and onion (OCCASIONALLY a few carrots). The kitchen table would then be used to roll out the noodle dough, which was cut into large squares and added near the end of the stewing process. My guess would be that it was called "pot pie" because everything was thrown in the pot - the chicken and the "dough". Grandma also made a chicken, gravy, and vegetable filled crusted pie that was just called Chicken Pie.
How is this a pie?