heirdom vs heirloom

heirdom

noun
  • An inheritance or succession. 

heirloom

noun
  • A valued possession that has been passed down through the generations. 

  • An old crop variety that has been passed down through generations of farmers by seed saving and cultivation, in contrast to modern cultivars used in large-scale agriculture. 

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