Originally Posted by http://www.answers.com/topic/alternative-words-for-british
The term Pommy for an British person is commonly used in Australian English and New Zealand English, and is often shortened to Pom. The origin of this term is uncertain. A number of fake etymologies have sprung up, mostly along the lines that POM is an acronym for "Prisoner of Mother England" or somesuch, referring to the fact that the earliest Australian settlers were convicts, sentenced to transportation. None of these explanations bears up under scrutiny, and the use of acronyms is largely a late twentieth century phenomenon. A more likely etymology is that it is a contraction of "pomegranates", a former rhyming slang term for immigrants ("immigranate"). The use of the word 'Pom' may be considered mildly derogatory - some may use it to cause offence, but it is also used in other situations as a friendly derogatory term among people who know each other well, if one of them is English and the other Australian.
In South Africa the term 'Pom' may also be used, while Afrikaans speakers use the term rooinek (literally 'red neck', on account of the sunburnt skin).