Most likely of Arabic descent (Romanized as Xhimeena or Xhimina); it has the Arab feminine ending, and Spain had been heavily occupied by Moors and Arabs for several centuries up to the life and death of El Cid. It is highly reasonable to surmise that Jimena (especially when considering the gutteral "J" or "Xh" and the three consonant pattern) was passed on to women of Spanish descent - many "Spanish" words are Arabic in origin.