I think Seppo with "o" on the end sounds Aussie to me. It doesn't sound like the London style of talking. Septic for an American is London, so is Sherman as in Sherman tank.

The Aussie stuck O on the end of other nicknames too. For instance, Abo or Abbo for a Native Australian, Gyppo or Jippo for an Egyptian (WW1 and WW2) and on occasion Jappo for Japanese.

I suppose they could also call Arabs Arrabos or ‘Rabbos.

One London slang word I’ve wondered about is “sherbet” for a pint of beer. Anyone know the etymology ?