Nothing but it's original Iroquoian name!
Just a little bit of history about the true name...
Iroquoian word "Ontarí:io," meaning "great lake" or "beautiful water," and was in use by at least 1639, long before the province or city of Ontario were established.
Trump isn't insulting Canadians at all. The Canadians were honoring the Iroquoian and Wendat native Indians.
He is insulting native Americans on both sides of the lake. Ontarí isn't even English or French.
Yes. Iroquoian languages were spoken on both sides of the present-day U.S.–Canada border—the border came much later than the peoples and languages.
The broader Iroquoian language family included peoples in what are now:
° New York and parts of the northeastern United States: Mohawk, Oneida, Onondaga, Cayuga, Seneca, and Tuscarora
° Southern Ontario and the Great Lakes: Wendat (Huron), Petun, Neutral, and related communities
° The Southeast U.S.: Cherokee, whose language is also Iroquoian but geographically more distant
The name Ontario is generally connected to a Wendat/Huron term associated with the lake. The Wendat homeland was mainly in what is now southern Ontario, but their trade, migration, alliances, and conflicts extended into areas now within the United States.
So “Iroquoian” does not mean exclusively Canadian—and neither does the history of the Great Lakes.
The region’s Indigenous history predates the modern national border by thousands of years.