What does the Latin word illi mean?

"IL IL" doesn't mean anything in Latin, unless it's the number 49 written twice in Roman numerals, although even that is questionable since it violates the usual rules for subtractive writing. Writing a letter with smaller value to the left of a letter with larger value indicates subtraction, but the larger number should not be more than ten times the smaller. Since L (= 50) is more than ten times I [= 1], IL [= 50 - 1?] violates this rule. The usual writing for 49 would be XLIX [= (50 - 10) + (10 - 1)].