I thought taint was a double contraction of "it ain't"...least it was down south: e.g. "'tain't gonna rain today, Jimbo."
There's
"taint"- the real estate from back sack to bung hole
"taint"- rural American for "it is not", and
"taint"- what I tell the judge the other side is doing when they present anything vaguely critical of my client.