Argthtjtr

I am fishing for an explanation.
The term 'Pom' for an Englishman is used in Australia, New Zealand and South Africa. The common explanation is that it is derived from 'pomegranate' - saying the British have red cheeks or 'Prisoner of Her Majesty'.
Neither of these are satisfactory as 'Pom' only applies to the English, not the British in general or other red-faced immigrants who turn up. The 'prisoners theory falls flat because the term only came into use long after the transportation to Oz period.
Every Englishman who turned up at the end of the 19th century, when the term came into use, had with him a dog of small breed called a Pomeranian, pom-pom or toy-pom.
I can find no reference to this as being the origin of the term 'Pom'. Has anybody read of a theory like this?

According to World Wide Words, the theory about the pomegranate seem to be the more credible one, its real origin remains unclear for this outdated term:

• 
  Part of the reason for all these theories growing up is that there was for decades much doubt over the true origin of the expression, with various Oxford dictionaries, for example, continuing to say that there is no firm evidence for the pomegranate theory. That origin was described by D H Lawrence in his Kangaroo of 1923: “Pommy is supposed to be short for pomegranate. Pomegranate, pronounced invariably pommygranate, is a near enough rhyme to immigrant, in a naturally rhyming country. Furthermore, immigrants are known in their first months, before their blood ‘thins down’, by their round and ruddy cheeks. So we are told”. You will note that he had to explain the pronunciation that we would now take to be the usual one: in standard English it used not to have the first “e” sounded, with pome often rhyming with home.


• 
  It is now pretty well accepted that the pomegranate theory is close to the truth, though there’s a slight twist to take note of. H J Rumsey wrote about it in 1920 in the introduction to his book The Pommies, or New Chums in Australia. He suggested that the word began life on the wharves in Melbourne as a form of rhyming slang. An immigrant was at first called a Jimmy Grant (was there perhaps a famous real person by that name around at the time?), but over time this shifted to Pommy Grant, perhaps as a reference to pomegranate, because the new chums did burn in the sun. Later pommy became a word on its own and was frequently abbreviated still further. The pomegranate theory was also given some years earlier in The Anzac Book of 1916.


• Whatever your beliefs about this one, what seems to be true is that the term is not especially old, dating from the end of the nineteenth century at the earliest, certainly not so far back as convict ship da

Pom:

• British person): Australian from 1912. contraction of pomegranate, rhyming slang for immigrant (“imme-granate”).



• The older term of Jimmy Grant, meaning immigrant, became Pommy Grant as the Australian sun allegedly turned immigrants′ skin pomegranate red.



• 
  

  Folk etymologies also exist, for example:

  
  
  
  
  
  • A devolution of “Prisoner of His/Her Majesty” or “POHM”;
  
  
  • An acronym for “Prisoner of Mother England”.
  
  
  • An acronym for "Permit of Immigration".
  
  
  
  

(Wiktionary)

I am a London taxi driver & heard an interesting theory a while back. There used to be a prison called millbank prison (definitely)in Westminster & the prisoners being transported to Australia would be taken from millbank prison in row boats down the Thames to be transferred to sailing ships & onward to Australia. Some say POM (prison or prisoner of millbank) was either marked on their shirts or on the side of the rowing boats.
There is a pub on the old Kent Road called The World Turned Upside Down, (still there) apparently prisoners were given one last drink before going round the world to Australia.