I came across this in "Between Two Worlds" by Benjamin L. Gordon, published in 1952. It is the autobiography of a Lithuanian Jew who was born around 1870 and emmigrated to the US.

The author's father's great-grandfather took the surname Gordomy, form the village where he lived. It was changed to Gordon by the author's grandfather:

"In the latter part of the eighteenth century there lived an English [sic] nobleman in London named Lord George Gordon (1751-1792), son of the third duke of Gordon. He accepted the Jewish faith.... It was customary in those days for pious Jews to travel abroad, in order to see with their own eyes the actual living conditions of their brethren in the Diaspora, so Lord Gordon traveled to the lands where most of his new co-religionists lived. He visited the city of Vilna, known as the Jerusalem of Lithuania, and there he became known as the Ger Tseddek (the Righteous Proselyte). His name quickly became a byword in the Jewish world. Parents came to use his name when blessing their sons, and many families adopted his name as a surname. It was thus that my grandfather changed Gordomy to Gordon."