"Pommy is supposed to be short for pomegranate. Pomegrante [sic], 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! Hence again, pomegranate, and hence Pommy. Let etymologists be appeased: it is the authorised derivation."

D H Lawrence: Kangaroo [complete with typo!]