Poms.
Well, when the convicts were transported here, they had Store High In Transit printed on their...No no no, wrong bullshit, sorry.

A story goes that the convicts had POHM on their shirts for Prisoner Of His/Her Majesty.
Another story goes that a train of rhyming slang goes along the lines of - immigrant, Jimmy Grant, pomegranate, pommygrant, pommy.

Suffice to say that for some reason lost to us now, Australians call all English "Poms" or "Pommies".