1) Dutch surname 2) Patronymic surname 
Thys is a Dutch patronymic surname similar to Thijs, a being a very common nickname for Matthijs (Mattheus). The Dutch digraph ij and the y (`ij` without dots) were used interchangeably until the surname spelling fixations around 1810. The form `Thys` is particularly common in the Belgian province of Antwerp, while `Thijs` is most common in ...