From the U.S. state name, derived from a Siouan Native American word meaning 'people of the big canoes.'
Missouri as a given name belongs to the distinctly American tradition of using place names — particularly state and river names — for children, a practice that flourished in the 19th century and reflected a frontier culture's sense that geography was destiny and that the land itself was worth honoring. The name Missouri derives from the Siouan-speaking Missouri people, whose name likely meant something along the lines of "those who have dugout canoes" or "people of the big canoes" in neighboring tribal languages. The Missouri River, one of the great arteries of the continent, carried the name westward into national consciousness.
The state of Missouri, admitted to the Union in 1821 after the contentious Missouri Compromise, occupied a pivotal position in American history — the gateway to the West, the contested ground between free and slave territory, the origin point of the Oregon and Santa Fe Trails. Children named Missouri in the 1830s through 1880s carried all of that charged geography with them. The name appears in census records most heavily in Missouri itself and in neighboring states, a product of regional pride and the common practice of naming children after their birthplace.
Families who moved West from Missouri sometimes gave the name to daughters born along the way as a memorial to what had been left behind. Missouri as a personal name was never common in the way that Mary or Elizabeth were common, but it was entirely unremarkable in its era — part of a cohort that included Indiana, Virginia, Georgia, and Carolina, all states that became girls' names. Today it carries a striking, slightly eccentric quality: deeply rooted in American soil, completely unambiguous about its heritage, and unlikely to be shared with anyone else in the classroom.