A derogatory word used to refer to a Brit, derived from the acronym POME (Prisoner of Mother England).
Oi, that Pommie bastard stole all me chips.
A derogatory term started by Australians to describe recent British immigrants. There is no proof that it had to do with the acronym Prisoners of Her Majesty. It is more likely that it was an abbreviation of the word pomegranate and referred to the flush complexion of Brits (like a pomegranate's flesh) or it was chosen to rhyme with immigrant (like "Larry Flint").
Hey look, it's white trash, two pommies and a yid.