SCHTUP?
I believe that is a well known, widely used Southern term. It is meant to stifle the other half of most any argument. It is pronounced as a two syllable word, Scht - up.

ie:(an attempt to keep this music related)
1st guy:You play notes on that there gittar with the Columbus method....first ya find the note and then ya land on it!!!
2nd guy:SCHT-UP!! You cain't do no better!