The derogotry part of Tank when refering to Yanks hasn't been used by any of U it's a term i don't use as why throw insults at a person u know nothing about the full insulting title is Septic tank quite a common site in Aus where towns don't have a piped water supply it comes from the Aussie habit of using rhyming slang. Septic tank became common as an insulting name during the 60's when Yank servicemen came to Aus on R&R leave