What was Martin Luther's middle name?

He entered the University of Erfurt under the name "Martinus Ludher Mansfeldt." He likely did not have a middle name, as they were not customary in his time. However a baptismal name was often given after a Saint or biblical figure. In 1517, he changed his name from Luder to Luther, as did his parents because "Luder" as an old German Word has other negative meanings.