Kosta

As I've already said elsewhere, in Greek the full form would be "Kostas," but, as the "s" (or rather "sigma") is only used in the nominative (or subject) case, it tends to be regarded as tacked on. ("Kostas said," but "Kosta's house," "give this to Kosta" or "I see Kosta.") This is why Greek forms of Hebrew names like "Elijah," "Jonah" and "Judah" add the "s" ("sigma") ("Elias," "Jonas," "Judas")