Medical doctors have used the term for hundreds of years to refer to a space within the human body that lies in between blood vessels and organs, or in between individual cells.
In the mid-1990s, Delia Sherman, Ellen Kushner, Terri Windling, Heinz Insu Fenkl, Midori Snyder, Kelly Link, Gavin Grant, Gregory Frost, Theodora Goss, Veronica Schanoes, Carolyn Dunn, Colson Whitehead, and other American writers interested in fantastic literature found themselves commiserating over the common perception that the genre-oriented publishing industry found it difficult to market truly innovative fiction involving unusual, fantastical, or cross-genre elements—because the mainstream literary fiction field demanded stories based in realism, while the fantasy field demanded stories that mostly followed the standard conventions of sword and sorcery or high fantasy.
Yet it seemed to the authors that some of the best literature was that which did not quite fit tidily into either category but instead was being discussed in terms of more amorphous, "in-between" descriptors such as "magic realism", "mythic fiction", or "the New Weird".
Over a period of several years, Kushner and Sherman prompted ongoing discussion about the importance of cultivating artistic "in-betweenness" led to the formulation of the broad concept of interstitial art.
"[1] Though many of the stories are written by science fiction, fantasy, and horror writers and contain fantastic or supernatural elements, Interfictions is not a genre anthology.