The Wikipedia page seems to have all the . io does seem to stand for inputoutput , though the meaning is purely historical . <| sep |> Don ' t worry . It will all make sense to you soon enough . I felt the campaign was amazing actually . Sure there was a lot of backlash over certain things , but I believe Kojima executed it perfectly given what he had to work with in regards to the game being rushed to the shelves by Konami . The more I sat and thought about it , the more I loved it , and the more it all made sense to me . I can ' t imagine a different campaign that would have had the same impact with fans and the community . So have fun ! I wish I could play it over again and get the same feeling once it was done as I did on my first playthrough . I envy the fact you ' re about to experience it for the first time .