Visited New Zealand and people there referred to the British as Pommies. It seem to have a slight derogatory ring to the tone, but no one would really explain how the practice came about. One person suggested that it may be an acronym for Prisoner Of his/her Majesty (POHM -> POM) since Australia had a huge influx of prisoners. Would love to hear the story behind this. *Edit: Expanded on question...
I looked this up in the 1959 edition of Brewers (reprinted from 1870) and they state that British pink and white complexions remind one of the pomegranate.
This is the only explanation given - no mention of POHM or anything like that.