In the Hitchhiker's Guide to the Galaxy books by Douglas Adams, "Ix" is mentioned as Ford Prefect's school nickname, which in the language of Betelgeuse Five translates as "boy who is not able to satisfactorily explain what a Hrung is, nor why it should choose to collapse on Betelgeuse Seven particularly". (Ford left Betelgeuse Seven after the Great Collapsing Hrung Disaster.)
For L.Frank Baum, author of the Oz books, Ix was another fantasy country, which he wrote about in Queen Zixi of Ix, or the Story of the Magic Cloak (1905). The country of Ix is mentioned in The Road to Oz (1909) also, when Queen Zixi attends the birthday party of Queen Ozma of Oz, and The Magic of Oz (1919), when Kiki Aru in bird form flies over the country.