Illinois

The name Illinois comes from the French rendering of an Algonquian word used by the Miami-Illinois and other related peoples. French explorers Jacques Marquette and Louis Jolliet encountered the Illiniwek (or Inoca) confederation of tribes in 1673 and recorded their name in various forms: Ilinouek, Illinioüek, and Ilinois.

The word derives from the Miami-Illinois language term irenwe·wa or ilinwe·wa, which literally means "he speaks the regular way" or "ordinary speaker." The -we·wa suffix in Algonquian languages indicates "speaker" or "one who speaks," while iren- or ilin- refers to "ordinary," "regular," or "normal." This name was likely used by neighboring tribes to distinguish the Illinois-speaking peoples from others who spoke different dialects or languages.

French explorers adapted this indigenous name with French phonetic conventions and pluralized it using the French suffix -ois (pronounced "wah"), creating Illinois. The spelling stabilized in French colonial records, though the final -s is silent in both French and English pronunciation, a vestige of French orthographic rules. Earlier colonial documents show alternate spellings such as Ilinois, Illinoise, and Illiniwek.

The Illinois Territory was established in 1809, carved from Indiana Territory. The region entered the Union as the 21st state on December 3, 1818. The state's name honors the indigenous Illinois Confederation, a group of 12–13 Algonquian tribes including the Peoria, Kaskaskia, Cahokia, and Tamaroa, who historically inhabited the region before being displaced by European colonization and conflicts with other tribes.

The demonym Illinoisan adds the English suffix -an to the French-derived place name, creating a standard English descriptor for the state's residents. Some informal alternatives include "Illinoian" or simply "from Illinois," though Illinoisan remains the most widely accepted form.