Wordorigins.org

This is a catchphrase of Australian origin that expresses boredom and a bit of world weariness, a modern I have seen the elephant.

While it’s believed to have originated in Australia, the earliest known use of the phrase in print is from the United States, in a 1982 Associated Press story:

Miss Tewes, who has just divorced, says she doesn’t plan to get married at this time. Using an Australian expression, she says, “Been there, done that.”¹