Definition: interjection used to express disbelief
Baloney is thought to have originated as a variant of bologna (“a large smoked sausage of beef, veal, and pork”) in the early 20th century. Our earliest written evidence, found in a 1921 newspaper article from Altoona, Pennsylvania (written in mock-colloquial form) supports this: “We got here Saturday afternoon and got the best place in the camp which is right near the stashun wheir there is lots of janes that rolls their own kums down from lebunun where they make baloney and the janes aint got far to come to see us.”
By the late 1920s baloney (which is also spelled as boloney) was being used to indicate that the speaker felt some matter was nonsense.
It is perfectly proper
For English students
To indulge occasionally
In: “Oh, baloney!”
”It’s a lot of bunk”
And “I’ll say so,”
So long as they never
Split their infinitives.
Elmira Star-Gazette (Elmira, NY), 14 Sept. 1928