... The proper derivation of the word is from the Greek Katharos, "pure"; and, therefore, the correct spelling of the name is Catharine or Katharine. (The Standard Dictionary of Facts, Ruoff, 1922)

... The maiden martyr, whose name was chosen as the center of the allegory of intellectual religion, was Καθαρινή (Kathariné), Catharina in Latin, from a virgin martyr of Alexandria, whose history being unknown, became another recipient of a half-allegorical legend.  It is not found recorded earlier than the eighth century, and, indeed, the complete ignorance of the state of the Roman empire, shown by making her the daughter of a king of Egypt, argues its development at a very late period... (History of Christian Names, Yonge, 1884)