Green’s Dictionary of Slang

(US) used as a measure of insignificance, usu. in phr. that ain’t chopped liver.

1944		E. Wilson 6 Apr. [synd. col.] ‘What am I — chopped liver?’ is something Vera Shea also invented.
1949		J. Adams Curtain Never Falls 175: ‘You’ve been nice enough, but what am I, chopped liver or something?’ Jackie patted her hand: ‘Are you kiddin’?’.
1966		S. Kingsley Night Life 16: Two hundred and eighty million dollars in the Union’s welfare fund. That ain’t chopped liver.
1993		H.L. Gates Jr Loose Canons 10: The literary canon— now that ain’t chopped liver. Could be you don’t understand how big this thing is.
2006		H. Kaplan Ninety Degrees at 49 242: That ain’t chopped-liver. But it still ain’t an Academy Award.