Chesley, Ontario is named for S. Y. Chesley, full name Solomon Yeomans Chesley, who was a minor civil servant in Ontario's Indian Department. He was born in 1796 in Schodack, Rensselaer County, New York and died in 1880 in Ottawa, but he grew up in Cornwall, Ont. and that area from about the age of three. He had learned how to speak Mohawk as a child, and also spoke fluent French as well as English. There is more information about him in a biographical sketch in the Dictionary of Canadian Biography. In addition, the Archives of Ontario has microfilmed a few years' worth of a diary he kept and I was able to borrow it on interlibrary loan and got to read about half of it.
His father was Allsaints Chesley, a native of Kinderhook, NY, and Lena or Helena Yeomans or Youmans. This Chesley family originated in Kinderhook and is NO KNOWN RELATION WHATSOEVER to the Chesleys of New Hampshire. "Chesley" is, in this case, a corruption of an unknown French surname, because Allsaints' father was from France according to his marriage record in the Kinderhook Dutch Reformed Church; and also, Solomon himself in the 1871 Ontario census gave his nationality as French (in spite of the fact that he was half Dutch and his paternal grandmother was probably English, thus he could only have been one quarter French).