During the period of World War I in the United States, there was a rise of anti-German sentiment, and German-sounding foods were re-named. A hamburger was called “liberty sandwich.”
 
”[A] hamburger sandwich? Liberty sandwich, you know, is the latest way to express it” was printed in the San Diego (CA) Union on September 21, 1918. The old name came back after the end of the war.
 
Other sandwiches (besides hamburgers) were also sometimes called a “liberty sandwich” during World War I, and the exact kind of sandwich is not always clear. “Liberty Steak Sandwich” was printed in the Evening Telegram (Elyria, OH) on February 1, 1919.
   
There were other “liberty” renamings. A hamburger was also called a “liberty steak” and sauerkraut was called “liberty cabbage.”
 
The terms “freedom fries” (for french fries) and “freedom toast” (for french toast) were used during the 2003 invasion of Iraq.
   
       
21 September 1918, San Diego (CA) Union, “Round-A-Bout” edited by A. Roundabouter, pg. 4, col. 6:
What has become of the old-fashioned man who used to have the nerve to go into a restaurant and call for a hamburger sandwich? Liberty sandwich, you know, is the latest way to express it.
 
Newspapers.com
1 February 1919, Evening Telegram (Elyria, OH), pg. 2, col. 7 ad:
Liberty Steak Sandwich
(Busy Bee Restaurant.—ed.)
 
Newspapers.com
26 July 1919, El Paso (TX) Herald, “California Lifts Ban On Stockingless Bathers” by G. A. Martin, pg. 7, col. 4:
Where hamburger steak signs formerly cluttered up the California beaches, you see “Liberty sandwich” signs these days. Nobody sells hamburger, but it tastes just the same.
   
Newspapers.com
12 September 1919, The Daily Northwestern (Oshkosh, WI), “Huge Crowd at Fair,” pg. 15, col. 4:
There were more than 100,000 “hot dogs” consumed during the day, sandwich merchants estimated. Moreover, there were an equal number of “liberty” sandwiches, formerly hamburgers, disposed of, they said.
 
Newspapers.com 
19 November 1919, Bisbee (AZ) Daily Review “Fight Is Declared Draw,” pg. 3, col. 2:
... although it nearly broke its tether in getting outside of a humburger (Liberty) sandwich ...
 
Newspapers.com
3 March 1933, Uintah Basin Record (Duchesne, UT), “Japan’s War Hysteria,” pg. 2, col. 3:
If a small boy, forgetting himself for a moment, should order a hamburger sandwich, it is not unlikely that his whole family would be persecuted as German sympathizers, even though the boy’s two older brothers should be at the front. Everyone knew that a real patriot ate only “liberty” sandwiches.
 
Newspapers.com
24 December 1939, South Bend (IN) Tribune, pg. 4, col. 2:
STILL SANE.
Gratifying evidence of public stability is found in the result of an American Institute of Public Opinion poll to determine the popular attitude toward German culture as distinguished from the brand of politics now dominant in Germany. During the world war, it is recalled, it became “treasonable” for Americans to manifest liking for anything of German implication. Some of the results of that attempt to evade reality appear ludicrous in retrospect. In the culinary zone, particularly, there was a strong tinge of fantasy. It became treasonable to eat sauerkraut in this country and patriotic to consume sauerkraut under the name of “Liberty cabbage.” The ever-popular hamburger sandwich was also preserved for utilitarian use by changing its name to “Liberty sandwich.”
 
Urban Dictionary
liberty sandwich
The U.S. name for Hamburgers during the first world war.
Y’all wanna go grab a liberty sandwich over at Dixies’ BBQ?
#hamburger#liberty#sandwich#ww1#america#germany
by Meet The Man April 29, 2015
 
Twitter
Digital Commonwealth
@digicomMA
“What the Fluff?!” It’s National Fluffernutter Day! The recipe was invented in Somerville, MA during WWI and was initially known as the “Liberty Sandwich”
8:30 AM · Oct 8, 2019·Hootsuite Inc.