From The Art and Popular Culture Encyclopedia
True south is the direction towards the southern end of the axis about which the earth rotates, called the South Pole and located in Antarctica. Magnetic south is the direction towards the south magnetic pole, some distance away from the south geographic pole.
The etymology of "south" comes the Old English word suth, related to the Old High German word sund, and perhaps sunne in Old English, with the sense of "the region of the sun" (sun culminates in the south in the northern hemisphere).
"The South" usually refers to "regions or countries lying to the south of a specified or implied point of orientation, especially the southeastern part of the United States".