It strikes me as being one of those portmanteau words like "Holmescest" or "Wincest" to describe a sub-genre of erotic fanfiction featuring intense sibling relationships within a fandom where the principal characters were called something like Chico or Chicane or Chicago. I can even see the sort of thing it might be, too; something about twin sisters from a dark and mysterious background who are working as a circus knife-throwing act travelling through the early 20th century mid-West, fighting vaguely supernatural crime. One of them might be a shape-shifter.