My Fair Lady movie and British Slang
At the beginning of the My Fair Lady movie, there is a monologue of prof. Higgins like this:
Hear a Yorkshireman, or worse
Hear a Cornishman converse
I'd rather hear a choir singing flat
Chickens cackling in a barn
Just like this one
"Garn"!
But, what's the meaning of this "Garn"?
Garn is a orthographic approximation to Eliza's pronunciation of the phrase "Go on"!
Go on, however, has little to do with the literal meaning of those words: it is a lower-class colloquial expression which dismisses what the previous speaker has just said as false, incredible, or absurd.
Other readers can no doubt provide more examples from recent British speech.
My Fair Lady is a 1964 American musical film. I like this movie and Audrey Hepburn so much! :)