Word mod l -> ll     
A doubled consonant may be rendered by just the single  MEDIEVAL
illustr.em           V      1 1 PRES ACTIVE  SUB 1 S    
illustro, illustrare, illustravi, illustratus  V (1st) TRANS   [XXXBO]  
illuminate, light up; give glory; embellish; make clear, elucidate; enlighten;
illustr.em           ADJ    3 2 ACC S C POS             
illustris, illustre, illustrior -or -us, illustrissimus -a -um  ADJ   [XXXBO]  
bright, shining, brilliant; clear, lucid; illustrious, distinguished, famous;
illustr.em           N      3 3 ACC S M                 
Illustris, Illustris  N (3rd) M   [DLXEQ]    Late  uncommon
Illustrious, title of highest officers of late empire; (above Spectabiles);