Green’s Dictionary of Slang

1. (US) tedious chatter, unwanted advice.

1931		Irwin Amer. Tramp and Und. Sl. 15: Kabitz. – Unwanted, unwelcome advice.
1949		Monteleone Criminal Sl. (rev. edn) 136: kabitz Unwanted advice.
1962		Ragen & Finston World’s Toughest Prison 806: kibitz – Unwanted, unwelcome advice.
1968		K. Brasselle Cannibals 177: I winked at Winant, who by now was on to my kibitzes.

2. a conversation.

2005

J. Stahl I, Fatty 105: The morning after my boardwalk kibbitz with Schenck and Anger my head felt like I’d used it to crack walnuts.