From M-W Oline:

Pom
Pronunciation: 'päm
Function: noun
Australian & New Zealand, usually disparaging : POMMY

Also from M-W Online:

Pommy
Main Entry: Pom•my
Variant(s): or Pom•mie /'pä-mE/
Function: noun
Inflected Form(s): plural Pommies

Etymology: by shortening & alter. from pomegranate, alteration of Jimmy Grant, rhyming slang for immigrant

Australian & New Zealand, usually disparaging : BRITON; especially : an English immigrant


Most of the other sources in OneLook show the same.