Named for the man who invented it, not the bird. You can see through the upper spokes of the wheel the bulbous breech band of wrought iron on the rear of the gun that Mrs. Parthenia Leila Ellis noticed (in Chapter One, The Sector Without Fire).
The 20-pounder Parrott was a rifled cannon used on both sides, though mainly by the Union. Lieutenant Benjamin’s Battery E of the 2nd U.S. Artillery had Parrotts exclusively, though his were firing specially-machined 3-inch Hotchkiss shells in the defense of Fort Sanders. The Ninth Corps was low on 20-pounder ammunition.