“Baloney,” which means “nonsense,” apparently originated around 1894 as a spelling variant of bologna sausage (traditionally made from odds and ends of inferior meat), representing the popular pronunciation. It was also used in the ring, in early 20th century slang, to mean an inferior fighter.
The Oxford English Dictionary says about the baloney-bologna connection: “[Commonly regarded as from bologna (sausage) but the connection remains conjectural.]” In the US even Italian-Americans sometimes call the meat “baloney,” as the Italian pronunciation of Bologna (and many other words) is thought to be too difficult for Americans to master.
Bologna sausage was originally made in and exported from Bologna in central Italy. It is regarded as a humble food of dubious origins. It thus made a good metaphor for “junk” just as we now use “spam” to mean unwanted e-mail advertisements. An early use of “baloney” to mean nonsense was in the phrase, “It’s baloney no matter how thin you slice it,” popular in the 1930s.
Long ago, before bullshit or even BS was widely used in semi-polite society, it was often said, “You’re full of baloney.” It was also sometimes said, “That’s just baloney!” Or even, “Oh, baloney!” So it seems that baloney is a euphemism for more than “nonsense.”
There exists a theory that “full of baloney” may have originated from “full of blarney,” an Irish comment on someone quick of tongue. “Blarney” also means nonsense, or more specifically, smooth flattery, and comes from the name of a village in Ireland.
Bishop Fulton J. Sheen said, in a radio address in 1954: “Baloney is the unvarnished lie laid on so thick you hate it; blarney is flattery laid on so thin you love it.”
I think the Bishop got it right. But, as a food-lover, I remember with some nostalgia the taste of the baloney and Spam sandwiches I ate as a kid. Just with nostalgia, though; I have no desire to eat either one again.