Grandmother's maiden name is listed as Kowesnki. I have not been able to find any such surname. Do you have any idea on the correct spelling?
I have actually heard and known of people with the last name Kowenski. I know it is a Jewish surname. I am pretty sure the spelling of "Kowesnki" is a typo.
It seems that it is a Polish-Jewish surname, based on the evidence above.
Like I said before, it seems highly likely that the other spelling was a typo, seeming that only two letters have been switched.