Derogatory term used by British and especially Australians for all American nationals.
1) Short for 'Separatist', i.e. 1776 separation from the Kingdom of Great Britain.
2) Derived from rhyming slang (Septic Tank = Yank).
2) My grandad was stationed in Pacific with the seppos during the second world war.
3) Person A: I am from Hungary
Person B: Is that even a country? I know that Europe is a country...
Person C (to Person A): Don't worry, she's just another typical seppo.