Holy covers a lot of territory. Let us start out small, one meaning of the word holy is “set aside”. A dish used in the Mass is holy because it has been set aside for use in the Mass which is the perfect prayer, the perfect sacrifice with it’s infinite merit and grace. Israel was a holy people (not because of their righteousness) because God set them apart for Himself. We are called to be holy, one meaning of that call is that we be set aside for God’s use, hence the references to the Holy Sisters and the Holy Father. Yes, these people are righteous, but they are also set aside for God’s use, consecrated for His purpose.