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At baptism, if two given names were given to the child, the first given name was a spiritual, saint's name. The second given name was the secular or call name, i.e., "rufnamen", which is the name the person was known by, both within the family and to the rest of the world. This custom was originally adopted in Germanic and other regions in Europe from Roman Catholic tradition and continued by the Protestants in their baptismal naming customs.
http://www.kerchner.com/germname.htm
Angela Hitler was Adolph's half sister.