The mystery has been solved. For 2 years, I could never figure out where the nickname "Pennsylvania Mud Turtles" came from, but thankfully I have history buffs/majors in my group who are great at research.
According to a few letters from Private Oliver Wilcox Norton who was a member of the 83rd Pennsylvania, the name refers/originates from
" One of the Wildcats had a mud - turtle yesterday. He made a little secesh flag and tied it to his hind flipper and made him trabble with it, dragging it round in the dust. It made some sport ."
Essentially someone made a small confederate flag, tied it to the hind flipper of a mud turtle, and the turtle ran around with it on. It was more or less of a joke/inside joke for the 83rd Pennsylvania thus creating the nickname.