What is "ratramnus"

Ratramnus, (died c. 870) a Frankish monk of the monastery of Corbie, near Amiens in northern France, was a Carolingian theologian known best for his writings on the Eucharist and predestination. His Eucharistic treatise, De corpore et sanguine Domini (On the Body and Blood of the Lord), was a counterpoint to his abbot Paschasius Radbertus’s realist Eucharistic theology. Ratramnus was also known for his defense of the monk Gottschalk, whose theology of double predestination was the center of much controversy in 9th-century France and Germany. In his own time, Ratramnus was perhaps best known for his Against the Objections of the Greeks who Slandered the Roman Church, a response to the Photian schism and defense of the filioque addition to the Niceno-Constantinopolitan Creed.