Καπογιάννης (Kapogiannis in Greek) seems to be a combination of Καπο+γιάννης.
Γιάννης is a common Greek first name. However I could not find any meaning or place name for the word "καπο".
Often names of places or surnames do not mean anything specific. Therefore I cannot conclude to a meaning that the name "Kapogiannis" may have.