"Illinois", without the 's sound', is what the French named the Native American tribe that lived in that region.
When La Salle traveled up the Illinois River in 1679, he named it after the Native Americans he found living along its banks.
Illinois is a French spelling for the Illinois and Peoria Indian word “ilini,” the plural of which is “iliniwok,” meaning man or a warrior and also a possible member of the Illinois tribe.
When the word was anglicized, the English retained that part of the French pronunciation.
Discover 25 fun facts about Illinois' history and culture from HuffingtonPost.com.
Find out how all 50 states got their names from MentalFloss.com.