Complex sentence: The name first appeared in a document of 1146 mentioning the free nobleman (Edelfrei) Helenger of Frankenstein, but the beginning of the caslte is assumed to be at an earlier date because the erection of a defensive tower around 1100 is reported in various documents.
Split into simpler sentences: The name first appeared in a document of 1146 mentioning the free nobleman (Edelfrei) Helenger of Frankenstein. But the beginning of the caslte is assumed to be at an earlier date because the erection of a defensive tower around 1100 is reported in various documents.