Shit for brains. Cranial- pertaining to the head. Fecal- Pertaining to excrement. -itis: this is added in order to make the word more medically appropriate. Not to be confused with -itis in reference to the drowsy after effect of eating a large meal.
Boys who enjoy yaoi (a genre in Japan that contains sexual and/or romantic relations between two men); literally translates to "rotten boy"; corresponding female : fujoshi