guess: the "Opedee" is the old Pee Dee River, which runs from NW to SE through (IIRC) South Carolina, and is one of the rivers that Sherman's men had to cross, in the dead of winter, as they came north after Marching through Georgia. I don't know the song as well; when I sing it, it turns into one of the variants of "free a little bird as I can be". Thanks Stewie