The name Niagara first appears, in the form Onguiaahra, in the writings of Jesuit priest Jérôme Lalemant, Superior to the Huron Mission, in 1641. The word is clearly of aboriginal origin, but Lalemant says nothing about its meaning.

The name "Niagara" is widely attributed to the indigenous peoples of the region, specifically a branch of the Iroquois Confederacy known as the Niagagarega or Neutral Confederacy. The word itself has several interpretations in various Iroquoian dialects, most famously "Onguiaahra," which is commonly translated as "The Strait" or, more poetically, "Thunder of Waters." French explorer Samuel de Champlain was among the first Europeans to write about the falls in the early 1600s after hearing reports from native guides, but the first detailed European description is credited to the Belgian missionary Father Louis Hennepin in 1677. Hennepin's published accounts brought the falls to global attention, but he did not "name" them; he simply transcribed the name used by the people who had lived there for centuries. Over time, the French spelling evolved into the modern English "Niagara." The name essentially serves as a linguistic bridge between the ancient indigenous presence and the colonial history of the North American frontier.