eldership vs seniority

eldership

noun
  • The position or office of being an elder. 

  • Seniority; the state or condition of being older. 

  • The smallest administrative division in Lithuania, equivalent to a ward. 

seniority

noun
  • A measure of the amount of time a person has been a member of an organization, as compared to other members, and with an eye towards awarding privileges to those who have been members longer. 

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