What's the origin of the Australian term 'Pom' or 'Pommie' for an Englishman?

'Pommie' is the not-so-nice term used for the British and is widely used by the Kiwis and the Aussies. It comes from P.O.M.E., which means Prisoner of Mother England and was stitched on the shirts of the many prisoners shipped to Australia and New Zealand.

https://en.wikipedia.org/wiki/Glossary_of_names_for_the_British#Pommy_or_Pom

According to the Oxford Dictionary of Australian Colloquialisms the word derives from the similarity between 'immigrants' and 'pomegranate', the latter being adapted to pommygrant hence pommie or pom. This derivation is largely confirmed by the Cassell Dictionary of Slang. However, when I was serving with the Australian army in the late 1950s the generally held view was that the word Pom derived from the days of transportation, the letters POHM standing for 'Prisoner of His/Her Majesty'.

It is supposed to represent
Prisoner Of Mother England

Some English people resent being called Pommies

There is also a suggestion that it comes from pomegranate.
Perhaps referring to the 'rosy red' cheeks of sunburned immigrants.
http://www.snopes.com/language/acronyms/pommy.htm

The term was originally spelt P.O.H.M. and stands for Prisoner of her/his majesty.

Pom:

The term Pommy for a 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 red skinned fruit, which bears a more than passing resemblance to the typical pale complexioned Englishman's skin after his first few days living under the hot Australian sun. 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.

[reference for the above quotation no longer exists, but the information can be found at other links]

It dates back to when convicts were transported to the Colonies ie Australia. They were called "PRISONERS OF HIS MAJESTY POHM. Pronounced POMS. I have only ever heard Australians use this term.

Florid indeed, rhyming slang (quite popular back then) for immigrant sounds more like it.

http://www.worldwidewords.org/qa/qa-pom1.htm

A number of possible derivations are offered, as is often the case with widely-used terms. One often suggested is an Australian acronym for 'Prisoner of His/Her Majesty' or 'Prisoner of Mother England' to refer to those who were transported. (Both of these terms have an extra word, making the derivation hard to support). Another is from pomegranate, a reference to the colour of sunburned skin of English migrants in Australia.

http://www.urbandictionary.com/define.php?term=pom

According to British Naval records the term "Pommie" came about from the red "pom-pon" on the top of the hats of British sailors who were involved in the transfer of prisoners to the Colonies. It was used as a derogatory term, but has since become a generalised term for British people. The term pommy or pom is commonly used by speakers of Australian English and sometimes speakers of New Zealand English, South African English and Afrikaans.

https://en.wikipedia.org/wiki/Alternative_names_for_the_British#Pommy