My family includes Kovens, De Kovens, and Kovensky.
To the best of my knowledge, Kovensky (Yaakov and Sarah Goldberg) and respective siblings left "Russia", or Ukraine, probably Nicolayev on the Black Sea near Odessa, arriving in Western Canada (Winnipeg, Manitoba) around 1902. Their children later included my father, Maurice, as well as Samuel, Dora, Sylvia, Percy (Peretz), and Sadie.
Kovensky was shortened to Koven shortly afterward, and several years later mysteriously became De Koven. De Kovens from the United States passing through Canada have contacted us, and have the same first names inherited from ancestors.
A tenuous theory: De Koven appears to be a bona fide Dutch name. In the 17th century, Amsterdam was the financial centre of the world, and Dutch traders travelled down the Volga and into Russia. Russifying De Koven would have entailed dropping the "De" and adding an "sky" to Koven, to get Kovensky. It could then have morphed back to De Koven in Canada or the U. S. My father did not subscribe to this theory, however.