Note 108 — Chapter VII · THEORY OF THE MEDIÆVAL EMPIRE.
Reading edition
'Romanos enim vocitant homines nostræ religionis.'—Gregory of Tours, quoted by Ægidi, from A. F. Pott, Essay on the Words 'Römisch,' 'Romanisch,' 'Roman,' 'Romantisch.' So in the Middle Ages, Ῥωμαῖοι is used to mean Christians, as opposed to Ἕλληνες, heathens.
Cf. Ducange, 'Romani olim dicti qui alias Christiani vel etiam Catholici.'