"What am I? Chopped liver?" and "That ain't chopped liver!" ("not chopped liver") became popular phrases by at least the 1940s.
Wikipedia: Chopped liver
Chopped liver is a spread popular in Jewish cuisine.
It is often made by sautéeing or broiling liver and onions in schmaltz (i.e., rendered animal fat); adding hard-boiled eggs, salt and pepper to the sautéed liver and onions, and grinding that mixture. However other methods and materials exist and so the exact process and ingredients may vary from chef to chef.
Chopped liver is a common menu item in Kosher delicatessens in the U.S. and Canada. Chopped liver is often served with rye bread as sandwiches.
The liver used is generally calves' liver or chicken liver. Shortening or oil is often substituted for the schmaltz.
Because of the liver, chopped liver is high in protein but also high in fat and cholesterol. Thus, low fat, mock, and vegetarian versions of chopped liver exist that are frequently made of a combination or base of peas, string beans, eggplant, or mushrooms.
Chopped liver in popular culture
Because of its unusual taste and appearance, it is an acquired taste and not a favorite or comfort food with everyone at the dinner table. This has given rise to the popular Jewish-American expression "What am I, chopped liver?", signifying frustration or anger at being ignored on a social level.
An alternate explanation for the etymology of the "What am I, chopped liver?" expression is that chopped liver was traditionally served as a side dish rather than a main course. The phrase, therefore may have originally meant to express a feeling of being overlooked, as a "side dish."
(Historical Dictionary of American Slang)
chopped liver n. something trivial; something to be scoffed at. -- usu. in negative.
1954 Jimmy Durante Show (CBS-TV): Now that ain't chopped liver.
1983 Family Feud (ABC-TV)(May 6): Now this is not exactly chopped liver.
1989 N.Y. Times Mag. (Dec. 3) 102: That hurt me in the industry...and itticked me off. I thought, "What was I -- chopped liver or something?"
1990 H.L. Gates, Jr., in N.Y. Times Bk. Review (Mar. 25) 37: The literary canon -- now that ain't chopped liver.
The WPA Guide to New York City
New York, NY: Random House
New York, NY: Pantheon Books
JEWISH. Gefulte fish (spiced fish cakes, served cold); sour cream mixed with fruit, vegetables, or pot cheese; chopped liver, usually mixed with fried onions and chicken fat; kugel (potato or noodle pudding); noodles and cottage cheese.
5 April 1947, Gettysburg (PA) Times, pg. 3, col. 1:
TO MEET ZALE
By SID FEDER
New York, April 3 (AP) -- (...) The bash boulevardiers insist you could put on the second go-round of that hair-raiser in Moose Jaw, Sask., or Elephant Butte, N. M., and still draw a half-a-million dollars, which is not, as the boys say, chopped liver.
The Curtain Never Falls
By Joey Adams
New York, NY: F. Fell
You've been nice enough, but what am I, chopped liver or something?
January 1951, Brooklyn (NY) Yellow Pages, pg. 731, col. 3:
LITTLE ORIENTAL RESTAURANT INC
"FAMOUS FOR CHOPPED LIVERS"
STEAKS . CHOPS
1546 PitkinAv...DTms 2-8731
The Tender Trap
by Max Shulman and Robert Paul Smith
New York, NY: Dramatists Play Service
CHARLIE. (...) What am I -- chopped liver or something?
"But He Doesn't Know the Territory"
by Meredith Wilson
New York, NY: Putnam
"Those other names you threw at me were not chopped liver, you know."
by Sidney Kingsley
New York, NY: Dramatists Play Service
KAZAR. Two hundred and eighty million dollars in the Union's welfare fund. That ain't chopped liver.
14 May 1967, Lima (OH) News, "Show Beat: Phyllis Diller," pg. D5, col. 4:
And that's not chopped liver.
22 December 1971, Capital Times (Madison, WI), comic strip section, pg. 2:
SO WHAT AM I...
(Winthrop comic strip -- ed.)
4 April 1972, Charleston (WV) Daily Mail, "'Days Of Our Lives' Girl Kisses After 5-Year Wait," pg. 2B, col. 1:
So what is Susan, chopped liver?
16 August 1976, Bucks County Courier Times (Levittown, PA), pg. B19, col. 2:
And that, as they say, ain't exactly chopped liver.
New York (NY) Times
On Language; Enough Already! What Am I, Chopped Liver?
By WILLIAM SAFIRE
Published: October 25, 1998
WHAT AM I?
At a chic Washington cocktail party, Elizabeth Drew, author of ''Whatever It Takes: The Real Struggle for Political Power in America,'' accepted an hors d'oeuvre of chopped liver smeared on a cracker and asked: ''Chopped liver is delicious. Why do people derogate it so? As in the expression, 'What am I, chopped liver?' ''
The earliest use of this phrase in its derogatory sense -- that is, ''something trivial; something to be scoffed at'' -- in the Random House Historical Dictionary of American Slang is by Jimmy Durante on his 1954 CBS-TV show: ''Now that ain't chopped liver.''
In a 1980 monologue about the Reagan-Carter Presidential debate, Johnny Carson noted Ronald Reagan's statement that if all the unemployed were lined up, they would stretch from New York to Los Angeles. ''He came up with another one today,'' said Carson. ''If everyone on welfare were chopped liver, you could spread them on a line of Ritz crackers from here to Bulgaria.'' A decade later, the actor-producer Michael Douglas applied the phrase to himself, complaining about his secondary role in a movie: ''That hurt me in the industry as an actor, and it ticked me off. I thought, What was I -- chopped liver or something?''
This show-biz usage contributed to the treatment of the ethnic culinary delicacy (in Yiddish, gehakte leber) as an object of disdain. It may have also been influenced by its sense in underworld lingo as ''a beaten and scarred person,'' or by the urbanization of the once-rural expression ''That ain't hay.'' Steinmetz speculates: ''Chopped liver is merely an appetizer or side dish, not as important as chicken soup or gefilte fish. Hence it was often used among Jewish comedians in the Borscht Belt as a humorous metaphor for something or someone insignificant.''
Nobody who tastes properly made chopped liver can use it as a derogation. I turned to my Times colleague Marian Burros, author of ''The New Elegant But Easy Cookbook,'' for the recipe: ''Saute one finely chopped medium onion in two tablespoons hot chicken fat until lightly golden and very soft. Add 1 pound chicken liver and saute until cooked through; process in food processor with one small raw onion and one hard-cooked egg. Season with salt and pepper and mix with enough chicken fat to make it moist and spreadable.''
Then you can say, ''I feel just as terrific as chopped liver!''