respublica Christiana

Etymology
First attested in : "Omnium enim christianorum una respublica est" ("For there is one commonwealth of all Christians"), De opere monachorum, 23.33. In early medieval usage, used chiefly to refer to the Byzantine Empire. From applied to the dominion of Frankish kings and emperors in the West. Generalised to refer to the community of all Christian states in the 11th century, which became the predominant meaning from the on.

Proper noun

 * 1) Christendom, the Christian nations as a political community.
 * 2)  The Christian empire, i.e. the Byzantine Empire or the Holy Roman Empire.
 * 1)  The Christian empire, i.e. the Byzantine Empire or the Holy Roman Empire.