Simply, I don't know. Used in answer to any question by someone who can't think of anything else to say. Used particularly by idiots from Australia, thinking it mocks Scotsmen in some way.
Andrew - Hi Rod, how are you today?
Rod - I don't rightly know.
Andrew, that's a shame, is it correct your an Australian idiot?
Rod - I don't rightly know
Rod - I don't rightly know.
Andrew, that's a shame, is it correct your an Australian idiot?
Rod - I don't rightly know
by Scottish Linguist March 19, 2015