Placidia is the Latin feminine from placidus (calm, gentle). **Galla Placidia (388-450 CE)** was the half-sister of Emperor Honorius — captured by Visigoths and married their king Athaulf, later returning to rule the Western Roman Empire as regent for her son Valentinian III.
Her mausoleum in Ravenna contains some of the finest preserved Late Roman mosaics.
Placidia reduces to seven — the number of Roman empress.