descent vs heirship

descent

noun
  • Lineage or hereditary derivation. 

  • A particular extension of the idea of gluing. 

  • A falling upon or invasion. 

  • A sloping passage or incline. 

  • A drop to a lower status or condition; decline. 

  • An instance of descending; act of coming down. 

  • A way down. 

heirship

noun
  • The status of being heir to something or someone 

How often have the words descent and heirship occurred in a corpus of books? (source: Google Ngram Viewer )