Only 11 years late, but I agree that it is a "Southern Thing".  While I grew up in Oklahoma, which is "sorta Southern", but not really, my father's family all settled in Mississippi after immigrating from Ireland, and lived there for a few generations before scattering further west.  At any rate, he used many "Southern" terms that few others in Oklahoma seemed to use.  I can only attribute that to his family's connection to Mississippi.  When he would pet his favorite cat, he would call her "Pitty Sang", which I, even as a small child, translated to "Pretty Thang" or, more properly, "Pretty Thing."  I had never heard anyone else use that term, until I read "A Good Man is Hard to Find" many years ago.  Until then, I had thought that was just my father's own unique term of affection.  So, perhaps not so unique, but certainly affectionate.